Micropump and method of using a micropump for moving an electro-sensitive fluid

ABSTRACT

The present invention provides a use of an electro-sensitive movable fluid, that is, a micromotor, a linear motor, a micropump and a method of using the micropump, a microactuator, and an apparatus which these devices are applied to, and a method and an apparatus of controlling flow properties of a fluid.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional of copending U.S. patent application Ser. No.09/020,725 filed Feb. 9, 1998, now U.S. Pat. No. 6,116,257 issued Sep.12, 2000.

FIELD OF THE INVENTION

The present invention relates to micromotors using electro-sensitivemovable fluids (electro-conjugate fluid, ECF) which move betweenelectrodes upon application of a voltage, and more particularly toextremely thin micromotors using the electro-sensitive movable fluids.The invention also relates to linear motors using the electro-sensitivemovable fluids. The invention further relates to micropumps using theelectro-sensitive movable fluids, methods of using the micropumps andmicroactuators using the micropumps as cooling means. The presentinvention furthermore relates to methods of controlling flow propertiesof substantially dielectric fluids by applying a voltage and apparatusesfor controlling flow properties of fluids.

BACKGROUND OF THE INVENTION

It is known that the characteristics of certain kinds of dielectricfluids vary when the dielectric fluids are subjected to electric fields.In case of liquid crystals, for example, when a voltage is applied toliquid crystal compounds, orientation properties of the compounds arevaried to thereby vary light transmittance of the compounds. It is alsoknown that, when a voltage is applied to heterogeneous fluids containingparticles or the like, properties of the fluids such as viscosity arevaried by Winslow Effect.

There are, however, problems in the fluids whose properties are variedupon application of a voltage. For example, the liquid crystal compoundsare very expensive, or the heterogeneous fluids show poor dispersionstability.

The present inventors have found such a novel effect that some specificfluids move upon application of a voltage, and already applied forpatents on the specific fluids (electro-sensitive movable fluids) andmicromotors using the electro-sensitive movable fluids (see: JapanesePatent applications No. 16871/1996, No. 16872/1996, No. 76259/1996, No.248417/1996 and No. 241679/1996), which form the basis of co-pendingU.S. patent application Ser. No. 08/792,544, filed Jan. 31, 1997. Themicromotors described in these publications show increased output powerwhen they are miniaturized.

In order to more efficiently drive the micromotors disclosed in theabove publications, they should be improved for the miniaturization. Themotors described in the publications are those of rotor rotation type,and any linear motor which is linearly driven is not described. Further,any pump using the electro-sensitive movable fluid is not describedeither.

When a voltage is applied to an electro-rheological fluid (ER fluid),its hydrodynamic properties such as viscosity greatly vary reversibly ata high speed correspondingly to the applied voltage. The fluids showingthese properties are broadly divided into heterogeneous type (particledispersion type) and homogeneous type. As the heterogeneous ER fluid, adispersion obtained by dispersing fine particles such as silica gel inan insulating oil is known.

The heterogeneous ER fluids, however, have a problem in thatsedimentation or flotation of particles takes place because of adifference in specific gravity between the particles and the medium.Even if the particles and the medium have the same specific gravity, thesame problem of sedimentation or flotation of particles takes place withtime because the temperature dependence of the specific gravity of theparticles and that of the specific gravity of the medium are differentfrom each other at low or high temperatures. Moreover, the dispersedparticles of the heterogeneous ER fluid form a chain structure when avoltage is applied, and therefore, the hydrodynamic properties of thefluid are changed. With the formation of the chain structure, not onlyincrease of viscosity but also development of elasticity takes place,and the fluid exhibits mechanical response approximate to a solid state.For this reason, linear control of the heterogeneous ER fluids isdifficult, and in many cases, complicated control means such as feedbackcontrol is necessary.

Of the homogeneous ER fluids, a liquid crystal is known as an ER fluidwhich exhibits no elasticity. The homogeneous ER fluids have ease ofcontrolling because they exhibit no elasticity even when a voltage isapplied, and they are free from problems of particle sedimentation andparticle flotation because they are homogeneous. However, thehomogeneous ER fluids such as liquid crystals are very expensive, sothat they are not broadly employed for an industrial use, liquidcrystals are only used for, for example, display devices of extremelyhigh value added. Further, the liquid crystals which are the homogeneousER fluids can be driven only in such a temperature range that the liquidcrystals are in the liquid crystal state, so that the temperature rangewherein the liquid crystals can be used as the ER fluids is extremelynarrow. Though the estimated temperature range wherein the ER fluids areused is from about −30° C. to about 120° C., the liquid crystals cannotbe driven in such a wide temperature range.

As described above, the homogeneous ER fluids are advantageous as the ERfluids from the control viewpoint, but they are very expensive and theirworking temperature range is narrow. On the other hand, theheterogeneous ER fluids are relatively inexpensive, but they aredifficult to control and have a problem of fluid stability such asoccurrence of particle sedimentation or particle flotation.

In the paper No. 96-252, pp. 437-438, of the 8th symposium on “Dynamicsrelating to Electromagnetic Force”, there is description about“Researches on Electrostatic Devices (New Stress-Transfer System UsingFibers)”. The particles dispersed in the heterogeneous ER fluid form achain structure when a voltage is applied to the heterogeneous ER fluid,as described above. This mechanism is applied to the electrostaticdevices of the above paper. That is, instead of the particles, anelectrode provided with woven fabric on its surface is used in a siliconoil, and a voltage is applied to the “woven fabric electrode”, whereby achain structure equivalent to the particle chain structure of theheterogeneous ER fluid containing particles is formed by the wovenfabric to thereby develop hydrodynamic properties of the ER fluid. Inother words, instead of using an ER fluid containing particles, using asilicon oil woven fabric free from sedimentation or flotation is bondedto an electrode material and the woven fabric is used as an electrode.By the application of a voltage, fibers of the woven fabric are allowedto stand up, and dynamic resistance of the upstanding woven fibers isproduced to control the fluid. Further, the manuscript collection (pp.203-206) of the 39th automobile control association lecture meeting(Oct. 16, 17, 18, 1996) discloses “New Torque-Transfer System UsingFibers”, and describes that, when fabric is adhesion bonded to acircular plate and the circular plate is rotated in an electric field,the shear stress is increased.

In the above methods, it is explained that the woven fabric has a rigidstructure upon application of a voltage and is orientated in thedirection of the electric field thereby to increase the shear stress. Inthe methods, therefore, the woven fibers which are swayed by the fluidwhen no voltage is applied are made rigid and orientated by applying avoltage, so that the fibers can resist the relative motion of the fluidto the electrodes, whereby increase of shear stress during applicationof a voltage is accomplished. In the methods, accordingly, only asilicon oil is used, and hydraulic oil constituting a machine part or aworking mechanism is never employed, further applicability of themethods to a mechanism.

In the above methods, further, the conductive electrode material is notexposed out at all and is evenly covered with the woven fabric.Moreover, there is no report about production of a jet flow. It isdescribed that the fibers of the woven fabric are swayed in thenon-electric field according to the shear rate. Accordingly, flowproperty control mechanism of the above methods is different from themechanism of the invention invented by the present inventors, that is,the shear stress is produced by virtue of formation of a jet flow. Theshear stress produced in the present invention has hydrodynamiccontinuity, is free from yield stress which indicates solidification andhas ease of controlling, while the above-mentioned fixed electrodesprovided with woven fabric do not show these properties.

OBJECT OF THE INVENTION

It is an object of the present invention to provide an extremelysmall-sized rotary motor and linear motor each of which is driven by ajet flow of an electro-sensitive movable fluid produced upon applicationof a direct-current-voltage and to provide a micropump using theelectro-sensitive movable fluid.

It is another object of the invention to provide a novel method of usingthe above-mentioned micropump.

It is a further object of the invention to provide a microactuator usingthe above-mentioned micropump as a cooling means.

It is a still further object of the invention to provide a method ofeasily controlling flow properties of a dielectric fluid in a widetemperature range, said fluid being a homogeneous fluid free fromsedimentation or flotation of particles, and to provide an apparatusemployable in the method.

SUMMARY OF THE INVENTION

The micromotor (thin micromotor) according to the invention is amicromotor comprising a container to be filled with an electro-sensitivemovable fluid, a lid to close the container by being engaged with theopen top of the container, a rotating shaft borne by a shaft holeprovided at the center of the lid and a bearing section provided at thecenter of the bottom of the container, a rotator fixed to the rotatingshaft and rotatable together with the rotating shaft, and electrodeswhich produce a jet flow of the electro-sensitive movable fluid uponapplication of a voltage, wherein the diameter of the rotator is largerthan the maximum thickness of the rotator.

The thin micromotor of the invention is broadly divided into a SE typeECF motor (stator-electrode type electro-conjugate fluid motor) and a REtype ECF motor (rotor-electrode type electro-conjugate fluid motor) withrespect to the position of the electrode provided therein. In the SEtype ECF motor, the electrodes are provided on the upper surface of thebottom and/or the lower surface of the lid of the container (fluidcontainer) and are in contact with the electro-sensitive movable fluid.In the RE type ECF motor, the electrodes are provided on the uppersurface and/or the lower surface of the rotator.

The housing of the micromotor of the invention generally has a maximumdiameter of 50 mm and a maximum height of several mm, and the micromotoris extremely small and particularly thin. In spite of such small size,the micromotor of the invention rotates at a high rotational speed ofabout several hundreds to several tens of thousands rpm.

The other micromotor according to the invention is a micromotorcomprising a housing constituted of a container to be filled with anelectro-sensitive movable fluid and a lid, an electro-sensitive movablefluid filled in the container, a rotor which rotates by detecting amotion of the electro-sensitive movable fluid that is moved uponapplication of a voltage, a rotating shaft to rotatably fit the rotor tothe housing, and plural electrodes which produce a jet flow of theelectro-sensitive movable fluid upon application of a voltage, whereinthe rotor is rotatably fitted to the housing through the rotating shaftand at least one bearing means. This micromotor includes the followingfirst to third micromotors.

The first micromotor (SE type ECF motor) of the invention is amicromotor wherein the rotor is a vane rotor having vanes for detectinga motion of the electro-sensitive movable fluid when theelectro-sensitive movable fluid is moved.

The second micromotor (RE type ECF motor) of the invention is amicromotor wherein the rotor is a cylindrical rotor whose surface isprovided with plural electrodes.

The third micromotor (cup type ECF motor) of the invention is amicromotor wherein the rotor is an open-bottom rotor having acylindrical body whose bottom is made open so as to allow theelectro-sensitive movable fluid to enter, and the plural electrodes arearranged on at least one surface selected from the group consisting ofan outer surface of the open-bottom rotor, an inner surface thereof, aninner wall surface of the housing and a wall surface of the protrudedbottom of the housing.

In the third micromotor (cup type ECF motor), the electrodes arearranged on at least one surface selected from the group consisting ofan outer surface of the open-bottom rotor, an inner surface thereof, aninner wall surface of the housing and a wall surface of the protrudedbottom of the housing. Therefore, the electrodes may be providedvertically on the inner wall surface of the housing as in theabove-mentioned SE type ECF motor, or may be provided vertically on theside wall of the protruded bottom.

That is, the micromotor of the invention includes the SE type ECF motor,the RE type ECF motor and the cup type ECF motor that is a complex typeof the SE type ECF motor and the RE type ECF motor. In the cup type ECFmotor, the rotor is in the cylindrical form whose top is closed andwhose bottom is open (in the form of a cup placed bottom upward), andhence this rotor is sometimes referred to as “open-bottom rotor” or “cuprotor” hereinafter.

By making the size of the micromotor of the invention smaller, theelectric energy can be converted to rotational energy with much higherefficiency. For example, when a SE type ECF motor whose housing has aninner diameter of 4 mm is used, the efficiency indicated by the ratio ofoutput energy/input energy has been confirmed to be at most 40%.

The linear motor according to the invention comprises anelectro-sensitive movable fluid, a container which is a closed containercontaining the electro-sensitive movable fluid, a driving shaft extendedfrom the container, a moving member which is linearly moved togetherwith the driving shaft by virtue of a jet flow of the electro-sensitivemovable fluid, and at least one pair of electrodes which produce the jetflow of the electro-sensitive movable fluid upon application of avoltage.

The linear motor of the invention is broadly divided into a SE type ECFlinear motor (stator-electrode type electro-conjugate fluid linearmotor), a PE type ECF linear motor (piston-electrode typeelectro-conjugate fluid linear motor) and a CE type ECF linear motor(complex-electrode type electrode-conjugate fluid linear motor), withrespect to the position of the electrode provided therein.

In the SE type ECF linear motor, the container (fluid container) has anouter cylinder and an inner cylinder; the electrodes are arrangedbetween the outer cylinder and the inner cylinder and function to forman ununiform electric field in the electro-sensitive movable fluid; andthe jet flow of the electro-sensitive movable fluid produced between theouter cylinder and the inner cylinder upon application of a voltagebetween the electrodes is introduced into the inner cylinder to therebymove the moving member in the inner cylinder.

In the PE type ECF linear motor, the moving member comprises at leastone pair of porous members through which the electro-sensitive movablefluid is able to pass; the pair of porous members are electricallyinsulated from each other and are fixed to the driving shaft; and anununiform electric field is formed in the electro-sensitive movablefluid by applying a voltage to the porous members to thereby produce ajet flow of the electro-sensitive movable fluid, whereby the porousmembers are moved together with the driving shaft in the container byvirtue of the reaction of the jet flow of the electro-sensitive movablefluid.

The CE type ECF linear motor is a complex type of the SE type ECF linearmotor and the PE type ECF linear motor. In the CE type ECF linear motor,for example, the fluid container has an outer cylinder and an innercylinder; at least one pair of electrodes is arranged in the innercylinder, and function to form an ununiform electric field in theelectro-sensitive movable fluid and further are reversible in theirpolarities; the moving member which is moved with the jet flow of theelectro-sensitive movable fluid produced upon application of a voltagebetween the electrodes is arranged between the outer cylinder and theinner cylinder; and the moving member is united to the driving shaftextended from the container.

The micropump according to the invention comprises an electro-sensitivemovable fluid and at least two electrodes which are arranged in such amanner that the electro-sensitive movable fluid is moved in thedirection of one electrode to the other electrode upon application of avoltage.

The method of using a micropump according to the invention comprises thesteps of arranging at least two electrodes in such a manner that anelectro-sensitive movable fluid is moved in the direction of oneelectrode to the other electrode upon application of a voltage, applyinga voltage to the micropump containing the electro-sensitive movablefluid, and producing a jet flow of the electro-sensitive movable fluidin the direction of a target.

The microactuator of the invention using the above-mentioned micropumpas a cooling means comprises an expansion pump chamber, suction anddischarge valves to suction and discharge a liquid from and to theoutside by expansion and contraction of the expansion pump chamber, anexpansion driving member made of a shape-memory alloy which iscontracted by electric power supply to expand or contract the expansionpump chamber, and a micropump comprising an electro-sensitive movablefluid and at least two electrodes which are arranged in such a mannerthat the electro-sensitive movable fluid is moved in the direction ofone electrode to the other electrode upon application of a voltage, saidmicroactuator serving to cool the shape-memory alloy with the jet flowof the electro-sensitive movable fluid produced by the micropump.

The micropump of the invention is designed so that the electro-sensitivemovable fluid is moved between the electrodes correspondingly to thevoltage applied between the electrodes, and serves as a pump by virtueof the self-propelled electro-sensitive movable fluid under applicationof a voltage. If a jet flow of the electro-sensitive movable fluid inthe direction of a target is produced and brought into contact with thetarget, the micropump of the invention can be used as a means to coolthe target when the temperature of the target is higher than thetemperature of the electro-sensitive movable fluid.

The method of controlling flow properties of a fluid according to theinvention comprises the steps of arranging at least one pair ofelectrodes capable of forming an ununiform electric field in a fluid,applying a voltage between the electrodes to produce a jet flow of thefluid between the electrodes, and controlling flow properties of thefluid by the jet flow.

The apparatus for controlling flow properties of a fluid according tothe invention includes in a fluid at least one pair of electrodescapable of forming an ununiform electric field, said electrodes beingarranged in such a manner that a voltage can be applied between theelectrodes and that a gap to be filled with the fluid is formed betweenthe electrodes.

At least one of the electrodes is preferably an uneven surface electrodehaving a non-smooth surface, particularly preferably a flockedelectrode.

If a pair of electrodes capable of forming an ununiform electric fieldin a fluid is arranged in the fluid and if a voltage is applied betweenthe electrodes, a new flow (jet flow) of the fluid, such as acirculating flow, is produced. When the shear direction of the originalmotion of the fluid is at right angles to the newly produced jet flow ofthe fluid, it is presumed that resistance to the relative motion of thefluid in the shear direction is produced, that is, shear stress isincreased.

When a certain kind of a dielectric fluid (i.e., “electro-sensitivemovable fluid” referred to herein) is subjected to an electric field, anelectric force is generated in the fluid owing to the ununiformity ofelectric conductivity and dielectric constant. In the direct-currentelectric field, the Coulomb force acting on space charge dominates thedielectrophoretic force. This Coulomb force causes hydrodynamicinstability, resulting in occurrence of convection of theelectro-sensitive movable fluid or a secondary motion of the fluid.These phenomena are known as “electrohydrodynamic (EHD) effects”.

The micromotor, the linear motor and the micropump according to theinvention use, as driving force, a motion (jet flow) of theelectro-sensitive movable fluid produced upon application of a voltageto the fluid. These control the flow properties or a fluid by forming anew jet flow from at least one pair of electrodes capable of formingununiform electric field in the fluid in a different direction, e.g.vertical and opposite direction, from that of the flowing fluid.

The present inventors consider that the motion of the electro-sensitivemovable fluid is probably by virtue of the EHD effects, but they do notconclude that the phenomenon occurring in the invention is owing to the“EHD effects”.

The micromotor, the linear motor and the micropump of the invention areapparatuses advantageously used to take out the flow energy of theelectro-sensitive movable fluid produced upon application of a voltageas driving force. That is, they are apparatuses to form a jet flow ofthe dielectric fluid by application of a voltage and to take out the jetflow as driving force. The micromotor of the invention is extremelysmall, and it can be made thin. Besides, the micromotor can be driven ata high speed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing a relation between conductivity and viscosityof the electro-sensitive movable fluid preferably used in the invention.

FIG. 2(A) is a vertical sectional view of the SE type ECF motor of theinvention, and FIG. 2(B) is a sectional view taken on line X—X of FIG.2(A).

FIG. 3(C) is a perspective view of the rotator, and FIG. 3(D) is asectional view taken on line Y—Y of FIG. 2(A).

FIG. 4(A) is a vertical sectional view of the RE type ECF motor of theinvention, and FIG. 4(B) is a perspective view of the rotator.

FIG. 5 is a view showing an embodiment of arrangement of the electrodesin the RE type ECF motor.

FIG. 6(A) and FIG. 6(B) are each a sectional view showing anotherstructure of the rotator.

FIG. 7 is a view showing a complex type micromotor of the SE type ECFmotor and the RE type ECF motor.

FIG. 8 is a sectional view of the micromotor having plural rotators.

FIG. 9 is a vertical sectional view of the SE type ECF motor, and FIG.10 is a sectional view taken on line A—A of FIG. 9.

FIG. 11 is a vertical sectional view of the RE type ECF motor, and FIG.12 is a sectional view taken on line A—A of FIG. 11.

FIG. 13(a) is a vertical sectional view of the cup type ECF motor, takenon line C—C of FIG. 14, and FIG. 13(b) is a vertical sectional view ofthe cup type ECF motor, taken on line D—D of FIG. 14.

FIG. 14 is a transverse sectional view of the cup type ECF motor (RE-REtype).

FIG. 15 is a schematic sectional view showing an embodiment ofarrangement of the electrodes in the cup type ECF motor of SE-SE type.

FIG. 16 is a schematic sectional view showing an embodiment ofarrangement of the electrodes in the cup type ECF motor of SE-RE type.

FIG. 17 is a schematic sectional view showing an embodiment ofarrangement of the electrodes in the cup type ECF motor of RE-SE type.

FIG. 18 is a graph showing a relation between applied voltage androtational speed, input power, output power or efficiency in two SE typeECF motors having different diameters.

FIG. 19 is a graph showing a relation among applied voltage, rotationalspeed and current in the SE type ECF motor having a diameter of 4 mm.

FIG. 20 is a vertical sectional view showing an embodiment of the SEtype ECF linear motor of the invention.

FIG. 21 is a view showing an embodiment of coil electrodes used in theSE type ECF linear motor.

FIG. 22 is a sectional view showing another embodiment of the SE typeECF linear motor.

FIG. 23 is a sectional view showing an embodiment of the PE type ECFlinear motor.

FIG. 24 is a sectional view showing an embodiment of the CE type ECFlinear motor.

FIG. 25 is a graph showing a relation between driving rate of a pistonand time in the SE type ECF linear motor.

FIG. 26 is a view showing another embodiment of the linear motor of theinvention.

FIG. 27 is a view showing an embodiment of a structure of the micropumpof the invention.

FIG. 28 to FIG. 30 are each a schematic view showing an embodiment ofshape of the electrode employable in the micropump of the invention.

FIG. 31 and FIG. 32 are each a view showing an embodiment of the pistondriving apparatus using the micropump of the invention as a coolingmeans.

FIG. 33 is a view showing the principle of driving the microactuatorincorporating the micropump of the invention as a cooling means.

FIG. 34 is a graph showing amplitude displacement given when theapparatus shown in FIG. 31 is used.

FIG. 35 is a graph showing variation of amplitude given when the powersupplied to the shape-memory alloy lines is varied to 0.5 W, 0.7 W, 0.9W or 1.1 W or 1.3 W.

FIG. 36 is a graph showing amplitude displacement given when theapparatus shown in FIG. 32 is used.

FIG. 37 is a view showing a structure of the microactuator used inExample 17.

FIG. 38 is a graph showing flow rate of the discharged liquid in themicroactuator used in Example 17.

FIG. 39 is a schematic view showing an embodiment of the controlapparatus preferably used in the invention.

FIG. 40 to FIG. 52 are each a graph showing viscosity of a fluid at eachshear rate in Example 18 to Example 30.

FIG. 53 is a schematic view showing an enlarged surface of a honeycombelectrode used in Example 30.

DETAILED DESCRIPTION OF THE INVENTION

The micropump according to the invention is described in detailhereinafter.

The electro-sensitive movable fluid for use in the invention is anorganic compound capable of forming a jet flow between the electrodescorrespondingly to the applied voltage, said organic compound beingliquid at its working temperature. This organic compound issubstantially dielectric.

The organic compound generally has at least one ester linkage in themolecule.

Listed below are examples of the compounds having the above propertiesand employable as the electro-sensitive movable fluid in the invention.

(1) Dibutyl adipate (DBA)

(2) Tributyl citrate (TBC)

(3) Monobutyl maleate (MBM)

(4) Diallyl maleate (DAM)

(5) Dimethyl phthalate (DMP)

(6) Triacetin

(7) Ethyl cellosolve acetate

(8) 2-(2-Ethoxyethoxy)ethyl acetate

(9) 1,2-Diacetoxyethane

(10) Triethylene glycol diacetate

(11) Butyl cellosolve acetate

(12) Butyl carbitol acetate

(13) 3-Methoxy-3-methylbutyl acetate (Solfit AC)

(14) Dibutyl fumarate (DBF)

(15) 2-Ethylhexyl benzyl phthalate

(trade name: Placizer B-8)

(17) Propylene glycol methyl ether acetate (PMA)

(18) Methyl acetyl ricinoleate (MAR-N)

(19) 2-Ethylhexyl palmitate

(trade name: Exepal EH-P)

(20) Dibutyl itaconate (DBI)

(21) Polyethylene glycol monooleate

(trade name: Emanone 4110)

(22) Butyl stearate

(trade name: Exepal BS)

(23) 2,2,4-Trimethyl-1,3-pentanediol diisobutyrate

(trade name: Kyowanol D)

(24) 2,2,4-Trimethyl-1,3-pentanediol monoisobutyrate

(trade name: Kyowanol M)

(25) Propylene glycol monoethyl ether

(26) Propylene glycol ethyl ether acetate

(trade name: BP-Ethoxypropyl Acetate)

(27) 9,10-Epoxy butyl stearate

(trade name: Sansocizer E-4030)

(28) Tetrahydrophthalic acid dioctyl ester

(trade name: Sansocizer DOTP)

(29) Tributyl phosphate (TBP)

(30) Tributoxyethyl phosphate (TBXP)

(31) Tris(chloroethyl) phosphate (CLP)

(32) Ethyl 2-methylacetoacetate

(33) 1-Ethoxy-2-acetoxypropane

(34) 2-(2,2-Dichlorovinyl)-3,3-dimethylcyclopropane carboxylic acidmethyl ester (DCM-40)

(35) Linalyl acetate

(36) Dibutyl decanedioate

(37) Mixture of Kyowanol M and Exepal EH-P in a mixing ratio of 1:4 byweight

Kyowanol M (trade name): 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate

Exepanl EH-P (trade name): 2-ethylhexyl palmitate

(38) Mixture of DAM and Exepal BS in a mixing ratio of 1:4 by weight

DAM (trade name): diallyl maleate

Exepal BS (trade name): butyl stearate

(39) Dibutyl dodecanedioate (DBDD)

Bu—OCO—(CH₂)₅—CH(Bu)—COO—Bu

(40) Dibutyl docosanedioate

Bu—OCO—(CH₂)₆—CH(CH₃)—(CH₂)₄—CH(CH₃)—(CH₂)₆—COO—Bu

(41) Daphne Super Hydraulic Fluid 32 (hydraulic oil) (Idemitsu KosanCo., Ltd.)

The compounds mentioned above can be used singly or in combination.

The conductivity and the viscosity of the above compounds, as measuredat 25° C., are set forth in Table 1.

TABLE 1 Conductivity Viscosity Compound ( ™: trade name) (S/m) (Pa · s)(1) DBA 3.01 × 10⁻⁹ 3.5 × 10⁻³ (2) TBC 5.71 × 10⁻⁷ 2.0 × 10⁻² (3) MBM2.60 × 10⁻⁵ 2.0 × 10⁻² (4) DAM 7.80 × 10⁻⁷ 2.5 × 10⁻³ (5) DMP 3.90 ×10⁻⁷ 1.2 × 10⁻² (6) Triacetin ™ 3.64 × 10⁻⁹ 1.4 × 10⁻² (7) Ethylcellosolve acetate 7.30 × 10⁻⁵ 9.0 × 10⁻⁴ (8) 2-(2-Ethoxyethoxy)ethyl6.24 × 10⁻⁷ 1.4 × 10⁻² acetate (9) 1,2-Diacetoxyethane 2.00 × 10⁻⁶ 1.5 ×10⁻³ (10) Triethylene glycol 5.20 × 10⁻⁷ 8.1 × 10⁻³ acetate (11) Butylcellosolve 2.10 × 10⁻⁵ 7.0 × 10⁻⁴ acetate (12) Butyl carbitol acetate5.20 × 10⁻⁸ 1.7 × 10⁻³ (13) Solfit AC ™ 8.30 × 10⁻⁸ 6.0 × 10⁻⁴ (14) DBF2.65 × 10⁻⁹ 3.5 × 10⁻³ (15) Placizer B-8 ™ 1.10 × 10⁻⁸ 7.8 × 10⁻² (17)PMA 1.56 × 10⁻⁷ 6.0 × 10⁻⁴ (18) MAR-N ™ 1.30 × 10⁻⁸ 1.4 × 10⁻² (19)Exepal EH-P ™  2.60 × 10⁻¹⁰ 9.5 × 10⁻³ (20) DBI 1.46 × 10⁻⁶ 3.5 × 10⁻³(21) Emanone 4110 ™ 3.75 × 10⁻⁷ 8.0 × 10⁻² (22) Expal BS ™  3.10 × 10⁻¹⁰8.5 × 10⁻³ (23) Kyowanol D ™ 6.24 × 10⁻⁹ 4.0 × 10⁻³ (24) Kyowanol M ™6.80 × 10⁻⁸ 1.2 × 10⁻² (25) MP-Ethoxypropanol ™ 2.24 × 10⁻⁵ 8.0 × 10⁻⁴(26) BP-Ethoxypropyl 3.10 × 10⁻⁸ 6.0 × 10⁻⁴ Acetate ™ (27) SansocizerE-4030 ™ 5.46 × 10⁻⁹ 2.0 × 10⁻² (28) Sansocizer DOTP ™  6.20 × 10⁻¹⁰ 4.0× 10⁻² (29) TBP 2.20 × 10⁻⁶ 2.2 × 10⁻³ (30) TBXP 1.10 × 10⁻⁵ 9.0 × 10⁻³(31) CLP 7.80 × 10⁻⁶ 3.0 × 10⁻² (32) Ethyl 2- 1.00 × 10⁻⁴ 5.0 × 10⁻⁴methylacetoacetate (33) 1-Ethoxy-2- 4.41 × 10⁻⁷ 4.0 × 10⁻⁴acetoxypropane (34) DCM-40 ™ 2.60 × 10⁻⁵ 5.5 × 10⁻³ (35) Linalyl acetate1.82 × 10⁻⁹ 1.3 × 10⁻³ (36) Dibutyl decanedioate 1.40 × 10⁻⁹ 7.0 × 10⁻³(39) Dibutyl dodecanedioate  5.2 × 10⁻⁹ 9.3 × 10⁻³ (40) Dibutyldocosanedioate 1.04 × 10⁻⁹ 2.5 × 10⁻² (41) Daphne Super Hydraulic   6.0× 10⁻¹⁰ 5.9 × 10⁻² Fluid 32 ™

The electro-sensitive movable fluid used in the invention is preferablya compound or a mixture each having the following specific conductivityand the following specific viscosity.

That is, when the conductivity σ and the viscosity η of the “dielectricfluids” including the above compounds are measured under the conditionsof an electric field intensity of 2 kVmm⁻¹ and a temperature of 25° C.,the dielectric fluids are distributed as shown in FIG. 1.

The compound used as the electro-sensitive movable fluid in theinvention is preferably a compound having, at its working temperature, aconductivity σ and a viscosity η located on or inside a triangle in agraph (FIG. 1) wherein the conductivity σ is plotted as abscissa and theviscosity η is plotted as ordinate, said triangle having the followingpoints P, Q and R as vertexes. When a mixture of two or more kinds ofcompounds is used as the electro-sensitive movable fluid, the mixture ispreferably such a mixture as adjusted to have a conductivity σ and aviscosity η located inside the above triangle.

TABLE 2 Conductivity (σ) Viscosity (η) Point P 4 × 10⁻¹⁰ S/m 1 × 10⁰ Pa· s  (Point P⁰) preferably preferably 5 × 10⁻¹⁰ S/m 8 × 10⁻¹ Pa · SPoint Q 4 × 10⁻¹⁰ S/m 1 × 10⁻⁴ Pa · S (Point Q⁰) preferably preferably 5× 10⁻¹⁰ S/m 2 × 10⁻⁴ Pa · S Point R 5 × 10⁻⁶ S/m  1 × 10⁻⁴ Pa · S (PointR⁰) preferably preferably 2.5 × 10⁻⁶ S/m    2 × 10⁻⁴ Pa · S

In Table 2, the points p⁰, Q⁰ and R⁰ are particularly preferable pointsas the vertexes of the triangle wherein the electro-sensitive movablefluid of the invention is located.

Some examples of the compounds preferably used as the electro-sensitivemovable fluid in the cooling method of the invention are given below.

(1) Dibutyl adipate (DBA)

(σ=3.01×10⁻⁹ S/m, η=3.5×10⁻³ Pa·s)

(6) Triacetin

(σ=3.64×10⁻⁹ S/m, η=1.4×10⁻² Pa·s)

(11) Butyl cellosolve acetate

(σ=2.10×10⁻⁸ S/m, η=7.0×10⁻⁴ Pa·s)

(12) Butyl carbitol acetate

(σ=5.20×10⁻⁸ S/m, η=1.7×10⁻³ Pa·s)

(13) 3-Methoxy-3-methylbutyl acetate (Solfit AC)

(σ=8.30×10⁻⁸ S/m, η=6.0×10⁻⁴ Pa·s)

(14) Dibutyl fumarate (DBF)

(σ=2.65×10⁻⁹ S/m, η=3.5×10⁻³ Pa·s)

(17) Propylene glycol methyl ether acetate (PMA)

(σ=1.56×10⁻⁷ S/m, η=6.0×10⁻⁴ Pa·s)

(18) Methyl acetyl ricinoleate (MAR-N)

(σ=1.30×10⁻⁸ S/m, η=1.3×10⁻² Pa·s)

(20) Dibutyl itaconate (DBI)

(σ=1.46×10⁻⁸ S/m, η=3.5×10⁻³ Pa·s)

(23) 2,2,4-Trimethyl-1,3-pentanediol diisobutyrate

(trade name: Kyowanol D)

(σ=6.24×10⁻⁹ S/m, η=4.0×10⁻³ Pa·s)

(26) Propylene glycol ethyl ether acetate

(trade name: BP-Ethoxypropyl Acetate)

(σ=3.10×10⁻⁸ S/m, η=6.0×10⁻⁴ Pa·s)

(27) 9,10-Epoxy butyl stearate

(trade name: Sansocizer E-4030)

(σ=5.46×10⁻⁹ S/m, η=2.0×10⁻² Pa·s)

(28) Tetrahydrophthalic acid dioctyl ether

(trade name: Sansocizer DOTP)

(σ=6.20×10⁻¹⁰ S/m, η=4.0×10³¹ ² Pa·s)

(33) 1-Ethoxy-2-acetoxypropane

(σ=4.41×10⁻⁷ S/m, η=4.0×10⁻⁴ Pa·s)

(35) Linalyl acetate

(σ=1.82×10⁻⁹ S/m, η=1.3×10⁻³ Pa·s)

(36) Dibutyl decanedioate

(σ=1.40×10⁻⁹ S/m, η=7.0×10⁻³ Pa·s)

(39) Dibutyl dodecanedioate (DBDD)

(σ=5.2×10⁻⁹ S/m, η=9.3×10⁻² Pa·s)

(40) Dibutyl docosanedioate

(σ=1.04×10⁻⁹ S/m, η=2.5×10⁻³ Pa·s)

(41) Daphne Super Hydraulic Fluid 32

(σ=6.0×10⁻¹⁰ S/m, η=5.9×10⁻² Pa·s)

When a mixture of plural compounds is used as the electro-sensitivemovable fluid in the invention, the conductivity and the viscosity ofthe mixture are made to be located inside the triangle defined by thepoints P, Q and R shown in FIG. 1, whereby the mixture can be preferablyused in the invention.

In other words, even if each of the compounds has a conductivity and/ora viscosity out of the above range, a mixture of the compounds can befavorably used as the electro-sensitive movable fluid in the invention,as far as the conductivity and the viscosity of the mixture are withinthe above range, respectively.

For example, a mixture (σ=2.60×10⁻⁹ S/m, η=9.8×10⁻³ Pa·s) of2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (trade name: Kyowanol M,σ=6.80×10⁻⁸ S/m, η=1.2×10⁻² Pa·s) and 2-ethylhexyl palmitate (tradename: Exepal EH-P, σ=2.60×10⁻¹⁰ S/m, η=9.5×10⁻³ Pa·s) in a mixing ratioof 1:4 by weight, each having a conductivity and a viscosity out of theabove range, can be favorably used as the electro-sensitive movablefluid in the invention. Also, a mixture (σ=4.17×10⁻⁹ S/m, η=5.0×10⁻³Pa·s) of DAM (diallyl maleate, σ=7.8×10⁻⁷ S/m, η=2.5×10⁻³ Pa·s) andbutyl stearate (trade name: Exepal BS, σ=3.1×10⁻¹⁰ S/m, η=8.5×10⁻³ Pa·s)in a mixing ratio of 1:4 by weight, each having a conductivity and aviscosity out of the above range, can be favorably used as theelectro-sensitive movable fluid in the invention.

The requisite of the electro-sensitive movable fluid is that the movablefluid has the above-defined conductivity and viscosity at its workingtemperature in the invention. That is, even the compounds having aconductivity and a viscosity out of the above range at 25° C. areemployable as the electro-sensitive movable fluids, as long as theconductivity and the viscosity of the compounds are within the aboverange at their working temperatures.

The electro-sensitive movable fluid does not particularly need tocontain other substances, but additives such as stabilizer,high-molecular weight dispersant, surface active agent andhigh-molecular weight viscosity increasing agent may be added. Further,compounds having no ester linkage can be used as the electro-sensitivemovable fluid, with the proviso that the conductivity and the viscosityof the compounds are located inside the above triangle.

Next, the thin SE type ECF motor using the electro-sensitive movablefluid is described.

FIG. 2(A) schematically shows a section of the thin SE type ECF motor ofthe invention. FIG. 2(B) is a sectional view taken on line X—X of FIG.2(A). FIG. 3(D) is a sectional view taken on line Y—Y of FIG. 2(A). FIG.3(C) is a schematic perspective view of a rotator.

The thin SE type ECF motor of the invention has a container 44 (bottomedfluid container) to be filled with an electro-sensitive movable fluidand a lid 41 which is engaged with the open top to close the fluidcontainer 44. When the lid 41 is engaged with the upper open part of thefluid container 44, the lid 41 and the fluid container 44 constitute aclosed housing 40.

The fluid container 44 for constituting the housing 40 has a bottom andis generally made of a material which is corrosion resistant to theelectro-sensitive movable fluid filled therein. Examples of suchmaterials include synthetic resins, such as polyolefins (e.g.,polyethylene and polypropylene), Teflon™, polycarbonate, acrylic resinand other engineering plastics; ceramics; woods; metals; and glasses.The fluid container 44 can be formed from a conductive material such asmetal (e.g., stainless steel). The fluid container 44 formed from aconductive material is preferably subjected to electrical insulationtreatment so as not to mar the insulated state between the electrodes,or the fluid container 44 is preferably formed from an insulatingmaterial.

The lid 41 is provided so as to close the open top of the mediumcontainer 44. The center of the lid 41 is provided with an upper bearingsection 46 by which a rotating shaft 45 is rotatably borne.

A lower bearing section 48 is provided at the center of a bottom 49 ofthe housing 40 to bear the lower end of the rotating shaft.

In the housing 40, a rotator 30 is incorporated. The rotator 30 isarranged so as to be rotated in the housing 40 together with therotating shaft 45. The rotator 30 is rotated by virtue of a jet flow ofthe electro-sensitive movable fluid 21 filled in the housing 40.

In the present invention, the rotator 30 is formed from a material whichis corrosion resistant to the electro-sensitive movable fluid filled inthe fluid container. Examples of such materials include syntheticresins, such as polyolefins (e.g., polyethylene and polypropylene),Teflon™, polycarbonate, acrylic resin and other engineering plastics;ceramics; woods; metals; and glasses.

In the SE type ECF motor, electrodes 50 a,b are provided on the lowersurface of the lid 41 for constituting the housing 40 and/or the innersurface of the bottom of the fluid container 44. In FIGS. 2(A), 2(B) and3(D), a SE type ECF motor wherein the electrodes 50 a,b are provided onboth of the lower surface of the lid 41 and the upper surface of thebottom of the medium container 44 is shown. The electrodes 50 a,b may beprovided on both of those surfaces as described above, or they may beprovided on one of the lower surface of the lid 41 and the upper surfaceof the bottom of the fluid container 44.

When the electrodes are arranged in such a manner that an ununiformelectric field is formed in the electro-sensitive movable fluid and avoltage is applied between the electrodes, a jet flow of theelectro-sensitive movable fluid is produced. Each of FIG. 2(B) and FIG.3(D) shows an embodiment wherein four positive electrodes 50 a arearranged radially from the center of the housing in such a manner thatthe angle between the adjacent positive electrodes becomes 90° and fournegative electrodes 50 b are arranged in such a manner the angle betweenthe negative electrode and the adjacent positive electrode becomes22.5°.

The electrodes 50 a,b may be formed by stretching conductor wires, butit is preferable that the electrodes 50 a,b are formed by utilizingplating technique adopted in the preparation of printed circuit boardsbecause the SE type ECF motor of the invention is extremely thin (e.g.,height of housing: 2 mm or less). By the use of the plating technique,the thickness of the electrode 50 a,b can be made not more than 100 μm,preferably 0.1 to 50 μm.

As described above, the electrodes 50 a,b are arranged in such a mannerthat an ununiform electric field is formed in the electro-sensitivemovable fluid 21. There is no specific limitation on the number of theelectrodes. The number thereof (total of positive electrodes andnegative electrodes) is in the range of usually 2 to 48, preferably 2 to36. The electrode 50 a,b is electrically connected to one end of aconductor 42 so that a voltage can be applied from the outside, and theother end of the conductor 42 is extended from the housing 40.

When the electrodes 50 a,b are provided on both the lower surface of thelid 41 and the upper surface of the bottom of the fluid container 44, ajet flow of the electro-sensitive movable fluid 21 is produced betweenthe adjacent electrodes, because the rotator 30 is present between theupper electrode and the lower electrode and therefore a jet flow of theelectro-sensitive movable fluid is hardly produced between the upperelectrode and the lower electrode. That is, a jet flow of theelectro-sensitive movable fluid is produced in the direction of an arrowas shown in each of FIGS. 2(A), 2(B), 3(C) and 3(D).

In the thin SE type ECF motor of the invention, the rotator 30 isrotated by the jet flow of the electro-sensitive movable fluid producedas above to thereby convert the electric energy applied to theelectrodes to rotational energy which can be taken out.

The rotator 30 is a circular plate fixed to the rotating shaft 45, andthe surface of the circular plate is provided with a flow receivingmember 31 to receive the jet flow of the electro-sensitive movable fluidand thereby rotate the circular plate. There is no specific limitationon the shape and the number of the flow receiving member 31, as far asthe jet flow of the electro-sensitive movable fluid can be received.Each of FIGS. 2(A), 2(B) and 3(C) shows an embodiment wherein six convexbars having a section of right-angled triangle are radially provided oneach of the front and the back surfaces of the circular plate. Ingeneral, flow receiving members 31 of usually 2 to 30, preferably 3 to20, are provided on the surface of the rotator 30, said surface facingthe surface of the housing 40 where the electrodes 50 a,b are arranged.The convex bars each having a section of right-angled triangle arearranged in such a manner that a side of the triangle, which is at rightangles to the Jet flow of the electro-sensitive movable fluid 21, is atright angles to the rotator. The flow receiving member 31 can beprovided so that this member protrudes from the circular plate (rotator30) as described above, or it can be provided in the concave form if thecircular plate has an appropriate thickness. The flow receiving member31 functions as resistance to the jet flow of the electro-sensitivemovable fluid 21 and rotates the rotator 30 together with the jet flow.Therefore, the flow receiving member 31 is not always a linear membersuch as the above-mentioned convex bar or concave line. For example, themember 31 may be a simple protrusion or a simple depression, or thesurface of the circular plate can be processed to have high surfaceroughness.

In each of FIGS. 2(A), 2(B), 3(C) and 3(D), an embodiment wherein therotator 30 is a flat circular plate is shown, but the rotator 30 can bemodified to have a vertical section of any of various shapes such asinverse triangle, rhombus and circle.

The center of the rotator 30 is fixed to the rotating shaft 45, and therotating shaft 45 is rotatably fitted to housing 40. The rotator 30, therotating shaft 45 and the optionally provided flow receiving member 31are formed from materials which are corrosion resistant to theelectro-sensitive movable fluid. Examples of such materials includesynthetic resins, such as polyolefins (e.g., polyethylene andpolypropylene), Teflon™, polycarbonate, acrylic resin and otherengineering plastics; ceramics; woods; metals; and glasses.

The rotator 30 is rotated in non-contact with the inner surface of thewall of the housing 40, and the ratio between the diameter of thehousing 40 and the diameter of the rotator 30 can be appropriatelydetermined. The electro-sensitive movable fluid between the outerperiphery of the rotator 30 and the inner surface of the wall of thehousing 40 is considered not to directly act on the rotational motion ofthe rotator 30, and hence the ratio between the diameter of the fluidcontainer 44 for constituting the housing 40 and the diameter of therotator 30. is in the range of preferably 100:99 to 100:50, particularlypreferably 100:95 to 100:75. In FIGS. 2(A) and 2(B), the diameter of therotator is relatively small for convenience sake, but in the SE type ECFmotor of extremely high efficiency, the diameter of the housing 40 andthe diameter of the rotator 30 are so approximate that the rotator 30 isnearly in contact with the inner wall surface of the fluid container 41.

The thickness of the rotator 30 (including a case where the flowreceiving member is provided) is in the range of usually about 0.05 to 5mm, preferably about 0.1 to 2 mm; the depth (i.e., distance between theupper surface of the bottom and the lower surface of the lid) of thehousing 40 to be filled with the electro-sensitive movable fluid 21 isin the range of usually about 0.5 to 10 mm, preferably about 1 to 2 mm;and the ratio between the height of the fluid container 44 and thediameter of the rotator 30 is in the range of usually 1:1 to 1:500,preferably 1:2 to 1:50.

The diameter of the housing 40 is in the range of usually about 3 to 50mm, preferably about 5 to 25 mm, and the SE type ECF motor of theinvention can be made extremely thin. Since the SE type ECF motor of theinvention is extremely thin, the amount of the electro-sensitive movablefluid contained therein is about 0.05 to 10 ml and is very small.

In the thin SE type ECF motor of the invention, the height of thehousing can be made usually not more than 20 mm, preferably not morethan 2 mm. In the thin SE type ECF motor, the height up to the tip ofthe rotating shaft can be made about 10 mm. Though the SE type ECF motorof the invention is extremely thin, the output power density representedby the ratio of torque/volume of the container is usually not less than1×10² W/m³, and the SE type ECF motor can be driven with much higherefficiency by making the size smaller.

Next, the thin RE type ECF motor is described.

FIG. 4(A) is a sectional view of the RE type ECF motor, and FIG. 4(B) isa perspective view showing arrangement of the electrodes provided on therotator. FIG. 5 shows another embodiment of the electrodes provided onthe rotator. In the RE type ECF motor and the above-described SE typeECU motor, the elements in common are given the same reference numerals.

In the thin RE type ECF motor of the invention, the basic constituentsare the same as those of the SE type ECF motor, but in the RE type ECFmotor, the electrodes are arranged on the rotator, differently from theSE type ECF motor. When a voltage is applied between the electrodes, ajet flow of the electro-sensitive movable fluid is produced, and byvirtue of the reaction of the jet flow, the rotator is rotated.

In the RE type ECF motor, a housing 40 is constituted of a fluidcontainer 44 to be filled with an electro-sensitive movable fluid 21 anda lid 41. In the housing 40, a rotator 30 is arranged. The rotator 30 isfixed to a rotating shaft 45, and the rotating shaft 45 is rotatablyfitted to the housing 40.

In the RE type ECF motor, the electrodes are not provided on the innersurface of the housing 40 but provided on the surface of the rotator 30as shown in FIG. 4(B).

In more detail, in the RE type ECF motor, the rotating shaft 45 and therotator 30 are united in one body, and the rotating shaft above therotator 30 is coated with a conductive film 45 a of a conductive metal.The conductive film 45 a continues to the joint to the rotator 30 and isfurther extended radially and linearly on an upper surface 30 a of therotator 30 toward a rim 33 of the rotator 30 to form electrode 50 a onthe upper surface 30 a of the rotator 30. The electrode 50 a which hasreached the rim 33 of the rotator 30 is then extended downward along therim wall and reaches the lower surface (back surface) 30 b of therotator 30. The electrode 50 a is further extended along thecircumferential direction, then is bent before an electrode 50 b on theback surface and is linearly extended in the axial direction, to formelectrode 50 a on the lower surface (back surface) 30 b.

On the other hand, the rotating shaft below the rotator 30 is coatedwith a conductive film 45 b. The conductive film 45 b continues to thejoint to the rotator 30 and is further extended radially and linearly onthe lower surface 30 b of the rotator 30 toward a rim 33 of the rotator30 to form electrode 50 b on the lower surface 30 b of the rotator 30.The electrode 50 b which has reached the rim 33 of the rotator 30 isthen extended upward along the rim wall and reaches the upper surface 30a of the rotator 30. The electrode 50 b is further extended along thecircumferential direction, then is bent before the linear electrode 50 aon the upper surface and is linearly extended in the axial direction, toform electrode 50 b on the upper surface 30 a.

The electrodes 50 a and 50 b are a positive electrode and a negativeelectrode, respectively, and they are electrically insulated from eachother.

FIG. 4(B) shows an embodiment wherein the positive electrodes 50 a andthe negative electrodes 50 b are extended radially from the center ofthe rotator. In this RE type ECF motor, the electrodes are arranged insuch a manner that an ununiform electric field is formed in theelectro-sensitive movable fluid, whereby a jet flow of the fluid isproduced. Therefore, there is no specific limitation on the arrangementof the electrodes and the shape thereof, as far as an ununiform electricfield can be formed in the electro-sensitive movable fluid. For example,the positive electrodes 50 a and the negative electrodes 50 b can bearranged so that a pair of the electrodes 50 a, 50 b is nearly inparallel to each other as shown in FIG. 5. In this case, if a fluidwhich forms a jet flow in the direction of one electrode to the otherelectrode (direction of the positive electrode 50 a to the negativeelectrode 50 b in FIG. 5) is used as the electro-sensitive movablefluid, the electro-sensitive movable fluid forms a jet flow in thecircumferential direction on the upper surface or the lower surface ofthe rotator 30 in the RE type ECP motor, and the rotator 30 is rotatedin the direction of the reaction of the jet flow (i.e., oppositedirection to the direction of the jet flow).

In the housing 40 of the RE type ECF motor of the invention, therotating shaft 45 is borne by the upper bearing section 46 and the lowerbearing section 48. Portions of the upper bearing section and the lowerbearing section, which are brought into contact with the conductive film45 a and the conductive film 45 b provided on the surface of therotating shaft 45, are formed from a conductive material. Theseconductive material portions are connected to the conductors 42, 42 sothat a voltage can be applied from the outside.

Though the electrodes 50 a, 50 b and the conductive films 45 a, 45 b canbe formed from various conductive materials, it is preferable that theyare formed by utilizing plating technique adopted in the preparation ofprinted circuit boards in view of the RE type ECF motor of the inventionbeing extremely thin and small. The electrodes 50 a, 50 b and theconductive film 45 a, 45 b are all extremely thin, and they have athickness of usually 0.01 to 30 μm, preferably 0.1 to 15 μm. The upperbearing section 46 and the lower bearing section 48 both can be formedby bonding a conductive metal, or can be formed by utilizing platingtechnique similarly to the above. The bearing sections 46, 48 and theconductive films 45 a, 45 b formed on the surface of the rotationalshaft 45 serve as contact points to supply a voltage. The bearingsections also serve as sliding points to rotate the rotator 30, andtherefore they are preferably provided with friction reducing means suchas ball bearing to inhibit decrease of rotational speed caused byfriction between the bearing sections and the rotating shaft. In case ofusing plating technique, solid components such as graphite, molybdenumdisulfide particles, Teflon™ particles and boron nitride (BN) particles,particularly solid lubricating components, are preferably added to theconductive materials containing gold, silver, copper or nickel, toreduce friction therebetween. When the conductive material haslubricating function or the solid lubricating component hasconductivity, both conducting properties and lubricating properties canbe obtained by plating only one component but of the above.

In FIGS. 4(A) and 4(B), the rotator 30 is in the shape of a flat plate.However, the shape of the rotator is not specifically limited and can beappropriately determined. For example, the rotator may have a verticalsection of inverse triangle as shown in FIG. 6(A), a vertical section ofrhombus as shown in FIG. 6(B), or a vertical section of circle.

The rotator 30 is rotated in non-contact with the inner wall surface ofthe housing 40, and the diametric ratio between the housing 40 and therotator 30 can be appropriately determined. The electro-sensitivemovable fluid 21 present between the outer periphery of the rotator 30and the inner wall surface of the housing 40 is considered not todirectly act on the rotational motion of the rotator 30, and hence theratio between the diameter of the fluid container 44 for constitutingthe housing 40 and the diameter of the rotator 30 is in the range ofpreferably 100:99 to 100:50, particularly preferably 100:95 to 100:75.In FIG. 4(A), the diameter of the rotator 30 is relatively small forconvenience sake, but in the RE type ECF motor of extremely highefficiency, the inner diameter of the fluid container 44 and thediameter of the rotator 30 are so approximate that the rotator 30 isnearly in contact with the inner wall surface of the fluid container 44.

The thickness of the rotator 30 is in the range of usually about 0.05 to5.0 mm, preferably about 0.1 to 1.0 mm, and the depth (i.e., distancebetween the upper surface of the bottom and the lower surface of thelid) of the housing 40 to be filled with the electro-sensitive movablefluid 21 is in the range of usually about 0.05 to 5.0 mm, preferablyabout 0.1 to 1.0 mm.

In the thin RE type ECF motor of the invention, the ratio between theheight of the rotator and the diameter of the rotator can beappropriately determined, and the ratio therebetween is in the range ofusually 1:1 to 1:500, preferably 1:2 to 1:50.

The RE type ECF motor of the invention can be made extremely thin.

In the thin RE type ECF motor of the invention, the height of thehousing 40 can be made usually not more than 20 mm, preferably not morethan 2 mm, and the height up to the tip of the rotating shaft can bemade about 10 mm. Though the RE type ECF motor of the invention isextremely thin, the output power density represented by the ratio oftorque/volume of the container is usually not less than 1×10² W/m³, andthe RE type ECF motor can be driven with much higher efficiency bymaking the size smaller.

The thin micromotor of the invention may be the SE type ECF motorwherein the electrodes are arranged on the housing 40, the RE type ECFmotor wherein the electrodes are arranged on the rotator 30, or acomplex type thereof. As shown in FIGS. 7(A), 7(B), 7(C), 7(D) and 7(E),the lower surface of the lid 41 of the housing 40 is provided withpositive electrodes 50 c and negative electrodes 50 d, and the surfaceof the bottom of the housing 40 is provided with positive electrodes 50e and negative electrodes 50 f. When the electrodes 50 c,d,e,f arearranged in the above way, a jet flow of the electro-sensitive movablefluid is produced predominantly between the.adjacent positive andnegative electrodes having a smaller distance. For example, if fourpositive electrodes are provided at an angle of 90° and if negativeelectrodes are each provided at an angle of 22.5° to the adjacentpositive electrode, a jet flow of the electro-sensitive movable fluid 21in the direction of the positive electrode to the negative electrode isgenerally produced. In this micromotor, a conductive film 45 a is formedon the surface of the rotating shaft 45 above the upper surface 30 a ofthe rotator 30 and a conductive film 45 b is formed on the surface ofthe rotating shaft below the lower surface 30 b of the rotator 30,similarly in the above-mentioned RE type ECF motor. Further, positiveelectrodes 50 g and negative electrodes 50 h extending from the rotatingshaft 45 to the rim 33 are provided on the surfaces of the rotator 30,similarly in the above-mentioned RE type ECF motor. Since the anglebetween the positive electrode 50 g and its negative electrode 50 h is22.5°, a jet flow of the electro-sensitive movable fluid 21 in thedirection of the positive electrode 50 g to the negative electrode 51 his produced between those electrodes. The thickness of the rotator 30 isrelatively large, and rim electrodes 50 j to connect the upper surface30 a of the rotator 30 to the lower surface 30 b thereof are providedobliquely on the surface of the rim wall of the roator 30. Therefore, ajet flow of the electro-sensitive movable fluid is produced also by therim electrodes 50 j. In this micromotor, electrodes 50 m and 50 n whichare adjacent to each other are provided also on the inner wall surfaceof the housing 40, so that a jet flow of the electro-sensitive movablefluid is produced also by the electrodes 50 m and 50 n. When thepolarities of these electrodes are set in such a manner that theresulting jet flows of the electro-sensitive movable fluid are in onedirection, the fluid can be moved at a higher velocity because of theresulting jet flows in one direction, and thereby the rotator 30 may berotated at a higher rotational speed.

As shown in FIG. 8, the micromotor of the invention can include pluralrotators 30 in the fluid container 44. FIG. 8 shows an embodiment of theRE type ECF motor wherein three rotators 30 are fixed to the rotatingshaft 45 and are rotatable in the housing 44.

The micromotor of the invention has a housing height of usually not morethan 20 mm and is extremely thin. By properly selecting arrangement ofthe electrodes, a material of the rotator, etc., the height of thehousing can be decreased to not more than 2 mm. Though the micromotor ofthe invention is extremely thin, it can be stably driven at a highrotational speed of about several hundreds to several tens of thousandsrpm.

Next, the other micromotor according to the invention is described.

FIG. 9 and FIG. 10 show an embodiment of a SE type ECF motor(stator-electrode type electro-conjugate fluid motor) that is the firstmicromotor of the invention.

The SE type ECF motor shown in FIG. 9 and FIG. 10 includes a container(bottomed cylindrical fluid container) 211 to be filled with anelectro-sensitive movable fluid 250, a lid 212 for the fluid container211, and a vane rotor 230 which rotates by detecting a motion of theelectro-sensitive movable fluid 250 with the vanes 231 when the fluid ismoved upon application of a voltage. A bottom 213 of the cylindricalfluid container 211 is provided with electrode insertion holes 241 tointroduce electrodes 240 a—240 h from the outside. The lid 212 isprovided with electrode fixing holes 242 to fix the electrodes 240 a—240h inserted through the electrode insertion holes 241 onto the inner wallsurface of the housing 210.

At the center of the lid 212, an upper bearing section 215 to bear arotating shaft 220 of the vane rotor 230 is provided.

The vane rotor 230 has plural vanes 231 arranged radially from therotating shaft 220, and the vane rotor 230 is fixed to the rotatingshaft 220 which is rotatably fitted to the housing 210 by the upperbearing section 215 and a concave bearing section 214 provided at thecenter of the bottom 213 of the fluid container 211. The vane 231 isusually in the shape of a flat plate, but it may be in any shape as faras it can efficiently detect a motion of the electro-sensitive movablefluid. For example, the vane can be in the curved shape in the flowdirection or in the shape of a ratchet.

The electrodes 240 a- - - 240 h are introduced into the fluid container211 through the electrode insertion holes 241 and extended upward alongthe inner wall surface of the fluid container 211 so as not to inhibitthe rotation of the vane rotor 230. The tips of the electrodes areinserted into the electrode fixing holes 242 and fixed therein.

The electro-sensitive movable fluid 250 is contained in the fluidcontainer 211 in such an amount that most of the vane rotor 230 isimmersed in the fluid, and a direct-current voltage is applied to theelectrodes 240 a- - - 240 h. Dummy electrodes where no voltage isapplied may be provided.

In the SE type ECF motor shown FIG. 9 and FIG. 10, the vane rotor 230having 8 vanes 231 is arranged in the cylindrical fluid container 211,and the electro-sensitive movable fluid 250 is filled in the fluidcontainer 211. When a voltage is applied between the electrodes 240a- - - 240 h which are arranged as shown in FIG. 10, the rotor 230begins to rotate. As the number of the vanes of the vane rotor 230 isincreased, the rotational speed tends to be increased. Further, as thedistance between the electrodes becomes narrower, or as the number ofthe pairs of the electrodes is increased, the rotational speed 231 tendsto be increased. The rotational speed of the vane rotor 230 is increasedor decreased proportionally to the applied voltage.

FIG. 11 and FIG. 12 are each a schematic sectional view of an embodimentof a RE type ECF motor (rotor-electrode type electro-conjugate fluidmotor) that is the second micromotor of the invention.

Referring to FIG. 11 and FIG. 12, the RE type ECF motor includes ahousing 210 constituted of a container (bottomed fluid container) 211 tobe filled with an electro-sensitive movable fluid 250 and a lid 212which is engaged with the open top of the fluid container 211 to closethe container 211. The lid 212 has a bearing means 216 and is engagedwith the open top of the fluid container 211 to constitute a closedhousing 210 together with the fluid container 211.

The center of the bottom of the fluid container 211 is provided with aconcave bearing section 214 to bear the lower end of a rotating shaft220. The concave bearing section 214 is provided with a rotationalcontact point means 246 for electrically connecting an external terminal248 to electrodes 240 a, 240 c, 240 e, 240 g. The rotational contactpoint means 246 is in contact with the lower part of the rotating shaft220 (lower rotating shaft 222 ). The rotational contact point means 246is filled with mercury 247 and sealed. The mercury 247 is brought intocontact with the lower rotating shaft 222. The concave bearing section214 is provided with a bearing means 216 to reduce friction between theconcave bearing section 214 and the lower rotating shaft 222.

The top of the fluid container 211 is made open to introduce theelectro-sensitive movable fluid 250 into the container.

After the fluid container 211 is filled with the electro-sensitivemovable fluid 250, the lid 212 is engaged with the open top of the fluidcontainer 211 to constitute the closed housing 210.

The center of the lid 212 is provided with an upper bearing section 215having a shaft hole through which the upper part of the rotating shaft220 (upper rotating shaft 221) penetrates. The upper bearing section 215is provided with a rotational contact point means 245 for supplyingpower to electrodes 240 b, 240 d, 240 f, 240 h. In the upper bearingsection 215, a bearing means 216 is incorporated to reduce friction tothe rotating shaft 220. From the rotational contact point means 245, aconductor is extended outside to form an external terminal 248. Also inthe rotational contact point means 245, mercury is filled as aconductive material.

Though the lid 212 is engaged with the fluid container 211 in FIG. 11,the lid 212 can be screwed on the container 211 to close the housing 210more firmly, or packing or the like can be inserted between the fluidcontainer 211 and the lid 212 to close the housing 210 more firmly.

The rotating shaft 220 is divided into the upper part (upper rotatingshaft 221) and the lower part (lower rotating shaft 222) by thecylindrical rotor 230 provided in the fluid container 211. The upperrotating shaft 221 and the lower rotating shaft 222 are electricallyinsulated from each other by means of an insulating material 223. Theupper rotating shaft 221, which penetrates the lid 212, is rotatablyborne by the upper bearing section 215 provided on the lid 212, whilethe lower end of the lower rotating shaft 222 is borne by the concavebearing section 214 provided at the center of the bottom of the fluidcontainer 211. Between the upper rotating shaft 221 and the lowerrotating shaft 222, the cylindrical rotor 230 rotatable together withthe rotating shaft 220 in the container 211 is arranged. The cylindricalrotor 230 is in the form of a cylinder having the rotating shaft 220 asits center axis of the rotation, and is arranged so that the rotor 230is not in contact with the inner surface of the fluid container 211 andthat a gap is formed between the rotor 230 and the fluid container 211.The ratio of the inner diameter of the fluid container 211 to thediameter of the cylindrical rotor 230 (inner diameter of fluid container211/diameter of rotor 230) is usually not less than 1.01, preferably1.05 to 10.0. For example, when the inner diameter of the fluidcontainer 211 is not more than 30 mm and the ratio of the inner diameterof the fluid container 211 to the diameter of the cylindrical rotor 230is in the range of 1.5 to 3.0, the rotor 230 is miniaturized so that therotational torque at the same rotational speed can be increased. Thatis, the efficiency of the RE type ECF motor can be increased by makingthe motor size smaller.

The shape of the rotor 230 is not limited to a cylindrical one, andvarious shapes such as a rectangular parallelepiped shape, a shapehaving a number of protrusions on the surface and a shape havingstar-like sections are employable according to the intended use. Thecylindrical rotor 230 may be hollow. In this case, the hollow portioncan be made vacuum or can be filled with air, gas, liquid or solid sothat the weight of the rotor is able to be optionally adjusted. Byadjusting the weight of the cylindrical rotor 230, the specific gravityof the rotor 230 in the electro-sensitive movable fluid 250 can beadjusted, whereby motion or balance of the rotor 230 can be controlled.

On the surface of the cylindrical rotor 230, electrodes 240 a, 240 c,240 e and 240 g connected to the upper rotating shaft 221 and electrodes240 b, 240 d, 240 f and 240 h connected to the lower rotating shaft 222are provided. The electrodes 240 a, 240 c, 240 e, 240 g and theelectrodes 240 b, 240 d, 240 f, 240 h can be formed by stretchingconductor wires on the surface of the cylindrical rotor 230. Theelectrodes 240 a, 240 c, 240 e, 240 g and the electrodes 240 b, 240 d,240 f, 240 h can be arranged at appropriate positions. FIG. 11 shows anembodiment of arrangement of the electrodes when the cylindrical rotor230 is seen from above. The electrodes 240 a, 240 c, 240 e, 240 g andthe electrodes 240 b, 240 d, 240 f, 240 h are arranged in such a mannerthat the interval angle θ between the electrodes is usually 1.0° to180°, preferably 3.0° to 90.0°. The interval angle θ varies depending onthe number of the electrodes arranged. Therefore, in order to set theinterval angle θ within the above range, the number of the electrodes240 a- - - 240 h is 2 to 120.

In FIG. 11 and FIG. 12, the electrode is extended from the electrodefixing hole 244 onto the surface of the cylindrical rotor 230, and thetip of the electrode is inserted into the electrode fixing hole 243 andis fixed therein.

The housing 210 having the above structure is filled with theelectro-sensitive movable fluid 250.

FIG. 11 and FIG. 12 show an embodiment of the RE type ECF motor whereinthe cylindrical rotor 230 formed from a tubular material is arranged inthe housing 210. The cylindrical rotor 230 is provided with a rotatingshaft 220 made of, for example, a metal bar.

A positive terminal and a negative terminal of a direct-current powersource are connected to external terminals 248, 248 in such a mannerthat a direct-current-voltage can be applied between the electrodes 240a, 240 c, 240 e, 240 g and the electrodes 240 b, 240 d, 240 f, 240 h ofthe RE type ECF motor. In this case, any one group of the electrodes 240a, 240 c, 240 e, 240 g and the electrodes 240 b, 240 d, 240 f, 240 h isset to be positive and the other is set to be negative. It isappropriately determined. Upon application of a direct-current-voltage,the electro-sensitive movable fluid 250 begins to flow, and with theflow (jet flow) of the electro-sensitive movable fluid 250, thecylindrical rotor 230 begins to rotate. The current given by applicationof the direct-current-voltage is very small and is usually not more than0.5 mA, in many cases not more than 20 μA, because the electro-sensitivemovable fluid is substantially non-conductive.

FIGS. 13(a), 13(b), 14, 15, 16 and 17 are each a schematic sectionalview showing an embodiment of a cup type ECF motor that is the thirdmicromotor of the invention. FIG. 13(a) is a schematic sectional viewtaken on line C—C of FIG. 14, and FIG. 13(b) is a schematic sectionalview taken on line D—D of FIG. 14.

Referring to FIGS. 13(a), 13(b) and 14, the cup type ECF motor includesa housing 210 to be filled with an electro-sensitive movable fluid 250and a cup rotor 230 which is rotatably fitted to the housing 210. Thehousing 210 is constituted of a fluid container 211 and a lid 212. Thefluid container 211 has a bottom 213 protruding upward inside the cuprotor 230. In the housing 210, the cup rotor 230, which covers theprotruded bottom 213 and is not in contact therewith, is rotatablyfitted to the housing 210 through a rotating shaft 220. On the outersurface and the inner surface of the cup rotor 230, electrodes 240, 240are provided so that they are brought into contact with theelectro-sensitive movable fluid 250 to be filled in the housing 210.

The fluid container 211 is constituted of a cylindrical body to form aside wall of the housing 210 and the bottom 213. The bottom 213functions to close the cylindrical body, and the central portion of thebottom 213 protrudes upward. The upper end of the protruded bottom isprovided with a lower bearing section 214 a. By the lower bearingsection 214 a, a lower part of the rotating shaft 220 (lower rotatingshaft 222) is rotatably borne. The lower bearing section 214 a isprovided with a rotational contact point means 246 which is filled withmercury 247 as a conductive material. The rotational contact point means246 is in contact with the lower rotating shaft 222. From the rotationalcontact point means 246, a conductor 248 for supplying power from theoutside power supply is extended. The lower bearing section 214 a isprovided with a bearing means 216 to reduce friction between therotating shaft 220 and the lower bearing section 214 a.

The top of the fluid container 211 is made open, and the lid 212 isengaged with the open top to close the housing 210. The center of thelid 212 is provided with an upper bearing section 215. By the upperbearing section 215, an upper part of the rotating shaft 220 (upperrotating shaft 221) is rotatably borne. The upper bearing section 215 isprovided with a rotational contact point means 245 which is filled withmercury 247 as a conductive material. From the rotational contact pointmeans 245, a conductor 248 for supplying power from the outside powersupply is extended. The upper bearing section 215 is provided with abearing means 216 to reduce friction between the rotating shaft 220 andthe upper bearing section 215.

The rotating shaft 220 is composed of the upper rotating shaft 221 andthe lower rotating shaft 222 which are electrically insulated from eachother by means of an insulating material 223. To the upper rotatingshaft 221, power can be supplied from the outside power source throughthe rotational contact point means 245 provided on the lid 212, while tothe lower rotational shaft 222, power can be supplied from the outsidepower source through the rotational contact point means 246 provided onthe lower bearing section 214 a.

The cup rotor 230 includes a rotor cylindrical body 234 with open bottomand a rotor lid 235. The rotor lid 235 serves to engage the rotorcylindrical body 234 with the rotating shaft 220 and functions as aconductor unit which is joined to the upper rotating shaft 221 and thelower rotating shaft 222 separately to supply power to electrodes 240.On the outer surface of the rotor cylindrical body 234, external firstelectrodes 240r2 - - - connected electrically to the upper rotatingshaft 221 and external second electrodes 240s1 - - - connectedelectrically to the lower rotating shaft 222 are provided. On the innersurface of the rotor cylindrical body 234, internal first electrodes240u2 - - - connected electrically to the upper rotating shaft 221 andinternal second electrodes 240u1 - - - connected electrically to thelower rotating shaft 222 are provided. In other words, the externalfirst electrode 240r2 is connected to the upper rotating shaft 221,passes through the electrode fixing hole 239 a provided at the rim ofthe rotor lid 235, then is extended vertically on the outer surface ofthe rotor cylindrical body 234, and the tip thereof is inserted into theelectrode fixing hole 239 b provided at the lower rim of the rotorcylindrical body 234 and is fixed therein. The external second electrode240s1 is connected to the lower rotating shaft 222, passes through theelectrode fixing hole 239 c provided near the upper end of the rotorcylindrical body 234, then is extended vertically on the outer surfaceof the rotor cylindrical 234, and the tip thereof is inserted into theelectrode fixing hole 239 d provided at the lower rim of the rotorcylindrical body 234 and is fixed therein. On the other hand, theinternal first electrode 240u2 is connected to the upper rotating shaft221, passes through the electrode fixing hole 239 d provided in therotor lid 235, then is extended vertically on the inner surface of therotor cylindrical body 234, and the tip thereof is inserted into theelectrode fixing hole 239 e provided at the lower rim of the rotorcylindrical body 234 and is fixed therein. The internal second electrode240u1 is connected to the lower rotating shaft 222, then is extendeddownward on the inner surface of the rotor cylindrical body 234, and thetip thereof is inserted into the electrode fixing hole 239 f provided atthe lower end of the rotor cylindrical body 234 and is fixed therein.

Accordingly, the external first electrodes 240r2 - - - and the internalfirst electrodes 240u2 - - - have the same polarity, and the externalsecond electrodes 240s1 - - - and the internal second electrodes240u1 - - - have the same polarity. The external electrodes are arrangedin the circumferential direction and generally in such a manner that apositive electrode and a negative electrode are alternately positioned.The internal electrodes are arranged in the circumferential directionand generally in such a manner that a positive electrode and a negativeelectrode are alternately positioned.

In the fluid container 211 having the cup rotor 230 therein, theelectro-sensitive movable fluid 250 is contained in at least such anamount that the cup rotor is immersed in the fluid, and the fluidcontainer 211 is closed with the lid 212. Then, the conductors 248, 248are connected to the outside power source, and a direct-current-voltageis applied. As a result, a jet flow of the electro-sensitive movablefluid 250 is produced, and thereby the cup rotor is rotated.

The cup type ECF motor (third micromotor of the invention) is describedabove with reference to the cup type ECF motor of RE-RE type whereinboth of the inner surface and the outer surface of the rotor cylindricalbody 234 are provided with electrodes, and this cup type ECF motor is acomplex one of the aforesaid SE type ECF motor and RE type ECF motor.With respect to the position of the electrodes arranged, the cup typeECF motor is divided into the following four types.

RE-RE Complex Type

As shown in FIG. 13 and FIG. 14, electrodes are provided on the innerwall surface and the outer wall surface of the cup rotor.

SE-SE Complex Type

As shown in FIG. 15, fixed electrodes are provided on the inner surfaceof the housing so as to be brought into contact with theelectro-sensitive movable fluid present outside the cup rotor, and fixedelectrodes are provided on the protruded bottom so as to be brought intocontact with the electro-sensitive movable fluid present inside the cuprotor.

RE-SE Complex Type

As shown in FIG. 16, RE electrodes are provided on the outer wallsurface of the cup rotor, and fixed electrodes are provided on theprotruded bottom so as to be brought into contact with theelectro-sensitive movable fluid present inside the cup rotor.

SE-RE Complex Type

As shown in FIG. 17, fixed electrodes are provided on the inner surfaceof the housing so as to be brought into contact with theelectro-sensitive movable fluid present outside the cup rotor, and REelectrodes are provided on the inner wall surface of the cup rotor.

In FIGS. 15 to 17, like elements are given like reference numerals. InFIGS. 15 to 17, the electrodes are indicated by numeral 243, and symbols“+” and “−” mean positive electrode and negative electrode,respectively. The arrangements of the electrodes described above areonly embodiments, and the present invention is not limited to thosearrangements.

The above-mentioned SE type ECF motor, RE type ECF motor and cup typeECF motor are only embodiments of the invention. The micromotor of theinvention can be variously modified.

As the size of the micromotor of the invention is smaller, the outputpower density becomes higher.

Next, the linear motor according to the invention is described.

In the linear motor of the invention, the aforesaid electro-sensitivemovable fluid is used.

FIG. 20 schematically shows a section of the SE type ECF linear motor ofthe invention. FIG. 21 schematically shows an embodiment of coilelectrodes used in the SE type ECF linear motor.

In the SE type ECF linear motor of the invention, electrodes arearranged in such a manner that an ununiform electric field is formed inthe electro-sensitive movable fluid. Upon application of a voltage, ajet flow of the electro-sensitive movable fluid is produced, and the jetflow is received by a moving member (piston) and is taken out as alinear motion.

The SE type ECF linear motor includes a fluid container 110 consistingof an outer cylinder 112 and an inner cylinder 114 provided in the outercylinder 112. The outer cylinder 112 has lids 116 a, 116 b at both ends,and the center of each lid 116 a, 116 b is provided with a shaft hole120 through which a driving shaft 118 penetrates. Between both ends ofthe inner cylinder 112 and the inner surfaces of the lids 116 a, 116 b,a gap is formed so that the electro-sensitive movable fluid is able toflow therein.

Coil electrodes 121, 122 shown in FIG. 21 are provided between the outercylinder 112 and the inner cylinder 114. The coil electrodes 121, 122are wound around the inner cylinder 114, and these electrodes 121, 121are insulated from each other. The coil electrodes 121, 122 are arrangedin such a manner that an ununiform electric field can be formed in theelectro-sensitive movable fluid 123. For forming an ununiform electricfield in the electro-sensitive movable fluid 123, it is advantageousthat the coil electrodes are arranged ununiformly, that is, as shown inFIG. 21, one electrode 121 and one electrode 122 are arranged at a shortdistance to give a pair, and the distance between one pair and the nextpair is made long. In FIG. 21, the distance between the pair ofelectrodes is 2 mm, and the distance between the electrodes which do notgive a pair is 4 mm, whereby an ununiform electric field is formed inthe electro-sensitive movable fluid. One end of each electrode thusarranged is extended out of the fluid container 110 so that a voltagecan be applied from the outside.

A moving member (piston) 125 is fixed to almost the center of a drivingshaft 118, and the moving member 125 receives a jet flow of theelectro-sensitive movable fluid 12 and is moved horizontally togetherwith the driving shaft 118 in the inner cylinder 114.

If the electrode 121 and the electrode 122 are set to be positive andnegative, respectively, and if dibutyl decanedioate is used as theelectro-sensitive movable fluid 123, the electro-sensitive movable fluid123 between the outer cylinder 112 and the inner cylinder 114 forms ajet flow in the direction of the arrow (in the left direction). Since agap wherein the electro-sensitive movable fluid 123 is able to flow isformed between the inner cylinder 114 and the lid 116 a, theelectro-sensitive movable fluid 123 flowing in the left directionbetween the outer cylinder 112 and the inner cylinder 114 is changed inits direction by the lid 116 a and then flows in the right direction inthe inner cylinder 114, to thereby move the moving member 125 in theright direction.

Then, the electrode 121 and the electrode 122 are set to be negative andpositive, respectively. The electro-sensitive movable fluid 123 flows inthe right direction between the outer cylinder 112 and the innercylinder 114, then the fluid 123 is changed in its direction by the lid116 b and flows in the left direction in the inner cylinder 114, tothereby move the moving member 125 in the left direction.

By the repetition of the above operations, the SE type ECF linear motorof the invention is linearly driven.

In the SE type ECF linear motor, positions of the coil electrodes andthe moving member can be reversed as shown in FIG. 22.

In the SE type ECF linear motor shown in FIG. 22, a fluid container 110is constituted of an outer cylinder 12, an inner cylinder 114, and lids116 a, a lid 116 b. On the inner surface of the inner cylinder 114, coilelectrodes 121, 122 are provided. Between the inner cylinder 113 and theouter cylinder 112, a ring moving member 125 a is arranged, and the ringmoving member 125 a is supported by auxiliary driving shafts 118 a, 118a branched from a driving shaft 118.

In the SE type ECF linear motors shown in FIG. 22 and FIG. 20, likeelements are given like reference numerals.

The SE type ECF linear motor shown in FIG. 22 is filled with theelectro-sensitive movable fluid 123 such as dibutyl decanedioate, and adirect-current-voltage is applied between the coil electrode 121 as apositive electrode and the coil electrode 122 as a negative electrode.As a result, a jet flow of the electro-sensitive movable fluid 123 inthe direction of right to left is produced in the inner cylinder 114.The jet flow impinges upon the lid 116 a, is changed in its direction,and enters into the gap between the outer cylinder 112 and the innercylinder 114, whereby the ring moving member 125 a is moved in the rightdirection. The motion of the ring moving member 125 a is transferred tothe driving shaft 118 through the auxiliary driving shafts 118 a, 118 a,and thereby the driving shaft 118 is moved in the right direction.

If the polarities of the coil electrodes are reversed, a jet flow of theelectro-sensitive movable fluid 123 in the opposite direction isproduced, and the ring moving member 125 a is moved in the leftdirection. As a result, the driving shaft 118 is moved in the leftdirection.

The linear motor of the invention may be a PE type ECF linear motor notusing the coil electrodes but using a pair of moving members aselectrodes. In this case, a jet flow of the electro-sensitive movablefluid is produced between the pair of moving members, and by virtue ofthe reaction of the jet flow, the PE type ECF linear motor is driven.

FIG. 23 shows an embodiment of the PE type ECF linear motor.

As shown in FIG. 23, the PE type ECF linear motor includes a cylinder132 for constituting a fluid container 110 and lids 136 a, 136 b whichare engaged with both ends of the cylinder 132 to close the cylinder132. The center of each lid 116 a, 116 b is provided with a shaft hole120 through which a driving shaft 118 penetrates and is horizontallymoved. To the driving shaft 118, a pair of moving members 141, 142through which the electro-sensitive movable fluid is able to pass arefixed in the vicinity of the center of the driving shaft. In FIG. 23,the pair of moving members 141, 142 (electrodes) through which theelectro-sensitive movable fluid is able to pass are made of metal wirecloth. Between the pair of moving members 141, 142, an insulating member143 is arranged, so that the moving members 141, 142 are insulated fromeach other.

When the electro-sensitive movable fluid 123 such as dibutyldecanedioate is subjected to an ununiform electric field, a jet flow ofthe movable fluid is produced in the direction of a positive electrodeto a negative electrode.

In FIG. 23, the driving shaft 138 is connected to an external terminal(not shown), and the moving member 141 and the moving member 142 are setto be a positive electrode and a negative electrode, respectively. As aresult, a jet flow of the electro-sensitive movable fluid 123 isproduced in the direction of the moving member 141 to the moving member142. In the PE type ECF linear motor shown in FIG. 23, theelectro-sensitive movable fluid 123 is able to pass through the movingmembers 141, 142, so that the moving members 141, 142 are moved in theopposite direction to the direction of the jet flow by virtue of thereaction of the jet flow produced upon application of a voltage. Whenthe moving member 141 and the moving member 142 in FIG. 23 are apositive electrode and a negative electrode, respectively, the movingmembers 141, 142 are moved in the left direction. Since the movingmembers 141, 142 are fixed to the driving shaft 138, the driving shaft138 is driven in the left direction with the motion of the movingmembers 141, 142.

There is no specific limitation on the shape, etc. of the moving members141, 142 serving as electrodes and as driving source of the PE type ECFlinear motor, as far as the moving members can be moved by the reactionof the Jet flow of the electro-sensitive movable fluid 123 produced uponapplication of a voltage. For example, a mesh moving member made ofmetal wire cloth shown in FIG. 23, a nozzle moving member and a ringmoving member are available. As the mesh moving member, metal wire clothhaving a mesh size of 0.05 to 5.0 mm, preferably 0.3 to 2.0 mm, isdesirable.

The linear motor of the invention may be a complex type of the SE typeECF linear motor shown in FIG. 20 and the PE type ECF linear motor shownin FIG. 23. The linear motor of complex type is referred to as “CE typeECF linear motor” hereinafter.

FIG. 24 shows an embodiment of the CE type ECF linear motor.

The CE type ECF linear motor shown in FIG. 24 has a fluid container 110similarly to the SE type ECF linear motor shown in FIG. 20. The fluidcontainer 110 is constituted of an outer cylinder 112, an inner cylinder114 arranged in the outer cylinder 112, and lids 116 a, 116 b engagedwith both ends of the outer cylinder 112. The center of each lid 116 a,116 b is provided with a shaft hole 120 through which a driving shaft118 penetrates. Between both ends of the inner cylinder 112 and theinner surfaces of the lids 116 a, 116 b, a gap is formed so that theelectro-sensitive movable fluid is able to flow therein.

Coil electrodes 121, 122 shown in FIG. 21 are provided between the outercylinder 112 and the inner cylinder 114 in such a manner that anununiform electric field is formed in the electro-sensitive movablefluid 123. By virtue of the coil electrodes 121, 122, a jet flow of theelectro-sensitive movable fluid 123 is produced between the outercylinder 122 and the inner cylinder 124. In FIG. 24, the electrode 121is a positive electrode and the electrode 122 is a negative electrode,so that the electro-sensitive movable fluid 123 such as dibutyldecanedioate forms a jet flow in the left direction between the outercylinder 112 and the inner cylinder 114. The electro-sensitive movablefluid 123 which flows in the left direction between the outer cylinder112 and the inner cylinder 114 is changed in its direction by the lid116 a and then flows in the right direction in the inner cylinder 114.

To the driving shaft 118, a pair of moving members 141, 142 (electrodes)are fixed in the vicinity of the center of the driving shaft. In FIG.24, the pair of moving members 141 and 142 through which theelectro-sensitive movable fluid is able to pass are made of metal wirecloth. Between the pair of moving members 141, 142, an insulating member143 is arranged, so that the moving members 141, 142 are insulated fromeach other.

When a direct-current-voltage is applied to the driving shaft 138 insuch a manner that the moving member 142 becomes a positive electrodeand the moving member 141 becomes a negative electrode, a jet flow ofthe electro-sensitive movable fluid 123 is produced in the innercylinder 114. By virtue of the reaction of the jet flow, the movingmembers 141, 142 are moved in the right direction. At the same time, thejet flow of the electro-sensitive movable fluid produced between theouter cylinder and the inner cylinder is introduced into the innercylinder and moves the moving members 141, 142 in the right direction.

When the polarities of the electrodes are reversed, the moving members141, 142 are moved in the left direction.

The linear motor of the invention is advantageous in miniaturization andis not specifically limited in its size. The linear motor of theinvention has a diameter of usually not more than 60 mm, preferably notmore than 30 mm, and a length of usually not more than 300 mm,preferably not more than 100 mm. From the studies of the rotary typemotors using the electro-sensitive movable fluid, it has been confirmedthat the liner motor of the invention can be driven with much higherefficiency by making the size smaller.

There is no specific limitation on the material for producing the linearmotor of the invention. Examples of the materials for the fluidcontainer and the moving member include synthetic resins (e.g., teflon,polycarbonate, acrylic resin), ceramics, woods, metals and glasses. Ifthese members are formed from a metal, the surface of the metal membersmay be subjected to insulating treatment if desired. The electrodes canbe formed from conductive metal wires or the like. The electrodes may beformed by plating used for printed board wiring.

The linear motor of the invention can be made to undergo reciprocatingmotion by changing the applied voltage. In the case where an externalforce is given to the moving member (piston), the linear motor can beused as a shock absorber to relax the external force by applying avoltage in such a manner that the piston is moved to resist the externalforce.

The linear motor can be variously modified.

In FIG. 26, the fluid container 110 is in the form of a loop, and theloop fluid container 110 is provided with electrodes 121, 122. When avoltage is applied between the electrodes 121, 122 to produce acirculating flow of the electro-sensitive movable fluid 123, thecirculating flow of the movable fluid 123 is received by a moving member125, whereby the moving member 125 is moved upward. On one surface ofthe moving member 125, a driving shaft 118 is provided, so that thedriving shaft 118 is vertically driven with the motion of the movingmember 125.

The micromotor and the linear motor according to the invention aredriven by filling an electro-sensitive movable fluid in a fluidcontainer and applying a direct-current-voltage of usually 50 V to 15kV, preferably 100 V to 10 kV, more preferably 100 V to 6 kV. Thecurrent given by application of a voltage is usually not more than 100μA, preferably 0.1 to 50 μA, particularly preferably 0.5 to 10 μA, sothat the power consumption is extremely small. Further, since thecurrent is extremely small, heat is hardly generated from the micromotoror the linear motor. Furthermore, since the micromotor and the linearmotor do not utilize magnetic force or magnetic field but utilize a jetflow of the electro-sensitive movable fluid produced in an electricfield, they are normally driven even in a strong magnetic field andgenerate none of magnetism, driving noise and electromagnetic noise.

Next, the micropump according to the invention is described.

The micropump of the invention has at least two electrodes. Theseelectrodes are arranged in such a manner that an electro-sensitivemovable fluid flows in the direction of one electrode to the otherelectrode. That is, the electrodes (jet flow-producing electrodes) arearranged in such a manner that an ununiform electric field can be formedin the electro-sensitive movable fluid. The ununiform electric field canbe formed by arranging the jet flow-producing electrodes, for example,in the following manner.

As shown in FIG. 27, two electrodes 320, 320 are arranged in a container351 containing an electro-sensitive movable fluid 314. When a voltage isapplied so that one electrode 320 becomes a positive electrode and theother electrode 320 becomes a negative electrode, the electro-sensitivemovable fluid 314 flows between the electrodes 320, 320. The micropumpof the invention is driven using, as its driving source, theelectro-sensitive movable fluid 314 which flows (is propelled by itself)between the electrodes 20, 20 under application of a voltage.Accordingly, there is no specific limitation on the arrangement, thenumber and the shapes of the electrodes, and they can be properlydetermined, as far as a uniform electric field is formed in theelectro-sensitive movable fluid by application of a voltage and therebythe electro-sensitive movable fluid moves between the electrodes to forma jet flow. In FIG. 27, for example, two bar electrodes 320, 320electrically insulated from each other are arranged at the center of thecontainer 351 containing the electro-sensitive movable fluid 14, butthese electrodes 320, 320 may be provided vertically on the innersurface of the wall of the container 351. The shape of the electrode isnot limited to the bar mentioned above. For example, referring to FIG.27, plate electrodes may be attached to the inner surface of the sidewall of the container 351. Though two electrodes are provided in FIG.21, electrodes of more than 2 can be provided. The number of theelectrodes may be an odd number.

The micropump shown in FIG. 27 comprises the closed container 351, theelectrodes 320, 320 provided in the container and the electro-sensitivemovable fluid 314, and produces a jet flow of the fluid 314 uponapplication of a voltage. This micropump functions as a circulating pumpwherein the electro-sensitive movable fluid is circulated in thecontainer 351. If a fresh electro-sensitive movable fluid 314 iscontinuously fed at the upstream side (e.g., left side in FIG. 27) ofthe flow of fluid 314 and if the electro-sensitive movable fluid 314 iscontinuously drawn out from the downstream side (e.g., right side inFIG. 27), the micropump of the invention functions as a transfer pump ofthe electro-sensitive movable fluid.

The shape of the electrode used in the micropump can be variouslymodified according to the intended use of the micropump.

For example, a nozzle electrode is prepared and a tapered electrodeinsulated from the nozzle electrode is provided in the vicinity of thebottom end of the nozzle electrode, as shown in FIG. 28, whereby themicropump of the invention functions as a jet pump wherein theelectro-sensitive movable fluid is jetted from the tip of the nozzleelectrode. The term “tapered electrode” used herein means an electrodeso designed to have a tip of an extremely small area. Examples of thetapered electrodes include a needle electrode (FIG. 28(a)), a linearelectrode (FIG. 28(b)) which is extended along the diameter of a nozzlehole of the nozzle electrode on its bottom end side, a point electrode(FIG. 28(c)) which is formed on a printed board arranged in the vicinityof the bottom end of the nozzle electrode, and a needlepoint holder typeelectrode (FIG. 28(d)) which is constituted of a substrate and pluraltapered electrodes (e.g., needle electrode, point electrode) providedthereon similarly to a needlepoint holder.

Examples of the nozzle electrodes used in combination with theabove-mentioned various tapered electrodes include an ordinary nozzleelectrode made of a conductive metal as shown in FIG. 28(a), a punchednozzle electrode obtained by punching a hole into a conductive plate,and a conical nozzle electrode (FIG. 28(d)) obtained by punching aconical hole into an insulating substrate and providing a conductivematerial on the conical wall surface.

The tapered electrode is preferably arranged in such a manner that thetip of the tapered electrode slightly enters into a nozzle hole. of thenozzle electrode on its bottom end side, as shown in FIG. 28(a). In themicropump of the invention having plural nozzle electrodes and pluraltapered electrodes arranged in the above-mentioned way, theelectro-sensitive movable fluid can be selectively jetted from thevoltage-applied nozzle electrodes in a high selectivity.

In the micropump of the invention, a multi-step electrode composed ofplural ring electrodes disposed in series as shown in FIG. 29 and FIG.30 is also available.

The multi-step electrode is obtained by disposing, in series, pluralrings (ring-electrodes) 371 a, 371 b, - - - , through which theelectro-sensitive movable fluid is able to flow. To the ring electrodes371 a, 371 b, - - - , a voltage is applied so that the electrodes becomepositive and negative alternately, as shown in FIG. 29(A). When avoltage is applied to the ring electrodes 371 a, 371 b, - - - , whichare disposed as above, a jet flow of the electro-sensitive movable fluidin the direction of the first ring electrode 371 a to the second ringelectrode 371 b is formed. This jet flow is accelerated when it advancesfrom the second ring electrode 371 b to the third ring electrode 371 c.The jet flow is further accelerated when it advances from the third ringelectrode 371 c to the fourth ring electrode 371 d. Consequently, theelectro-sensitive movable fluid can be moved at a higher velocity bymeans of the micropump of the invention wherein plural ring electrodesare disposed in series as described above. The ring electrode can beformed from, for example, a conductive metallic wire, as shown in FIG.29(B), or can be formed from a conductive metallic plate or metallicfoil having a hole through which the electro-sensitive movable fluid isable to pass, as shown in FIG. 29(C). Further, the ring electrode may beformed by subjecting the inner surface of an insulating cylindricalmaterial to conductive metal plating of circumferential directionutilizing such as printed wiring technique or plating technologies.

The ring electrode is preferably provided with an electrode protrusion372, which is electrically connected to the ring electrode, on thedownstream side of the jet flow, as shown in FIG. 29(A). Though theelectrode protrusion 372 may have various shapes, a needle shape ispreferable because the resistance to the jet flow of theelectro-sensitive movable fluid is low. The ring electrodes 371 providedwith the electrode protrusion 372 are arranged in series in such amanner that the electrode protrusion 372 is not in contact with the nextring electrode 371. By virtue of the electrode protrusion 372, the jetflow of the electro-sensitive movable fluid in the direction of theelectrode body to the electrode protrusion can be selectively formed.

The ring electrode can be modified to have a cylindrical body. That is,as shown in FIG. 30(A), the ring width (in the direction of the jetflow) of the ring electrode is enlarged in such a manner that the jetflow of the electro-sensitive movable fluid is not inhibited, to form acylindrical body 381 (cylindrical electrode). The cylindrical electrodeis preferably provided with an electrode protrusion 382 at its end onthe downstream side of the jet flow, similarly to the ring electrode.

Plural cylindrical electrodes 381, each of which is provided with theelectrode protrusion 382, are arranged in series in an insulatingcylinder 383 in such a manner that the electrodes are insulated fromeach other, whereby a jet flow of high velocity can be produced.

FIG. 30 shows an embodiment wherein the electrode positioned on the mostdownstream side of the jet flow is a nozzle electrode 384. When thenozzle electrode 384 is arranged at the tip of the pump as above, thispump functions as a jet pump of the electro-sensitive movable fluid. Ifthe cylindrical electrode is arranged at the tip of the pump, this pumpfunctions as a circulating pump or a transfer pump.

The micropump of the invention has no mechanical driving means and isdriven by merely applying a voltage to the electro-sensitive movablefluid, and therefore the micropump is advantageous in miniaturization.

The micropump of the invention is driven by applying a voltage betweenthe electrodes, and the applied voltage is, for example, a pulsevoltage, a rectangular voltage or a continuous voltage. Particularly, adirect-current-voltage of continuous wave is preferably applied in themicropump of the invention. The voltage applied between the electrodesis a direct-current-voltage of usually 50 V to 30 kV, preferably 100 Vto 15 kV. By adjusting the applied voltage, the output power of themicropump of the invention can be controlled. Even if a voltage isapplied, the current in the electro-sensitive movable fluid is extremelysmall, and therefore generation of heat caused by driving the micropumpis not substantially observed.

The micropump wherein the electrode positioned on the upstream side ofthe jet flow is a positive electrode and the electrode positioned on thedownstream side of the jet flow is a negative electrode is describedabove, but the electrode on the upstream side may be a negativeelectrode and the electrode on the downstream side may be a positiveelectrode according to the type of the electro-sensitive movable fluid.

Like the conventional pumps, the micropump of the invention can be usedas a transfer pump, a jet pump or a circulating pump.

In particular, the micropump of the invention is preferably used forheat energy exchange. That is, a voltage is applied to produce a jetflow of the electro-sensitive movable fluid toward a target, and thethus produced jet flow is brought into contact with the target, wherebyheat energy exchange is carried out utilizing temperature differencebetween the jet flow and the target. When the temperature of theelectro-sensitive movable fluid is higher than that of the target, themicropump of the invention can be used as a means to heat the target.When the temperature of the electro-sensitive movable fluid is lowerthen that of the target, the micropump of the invention can be used as ameans to cool the target.

FIG. 31 schematically shows an embodiment of a piston driving apparatususing shape-memory alloy lines 312.

In the piston driving apparatus, as shown in FIG. 31, a lower fixed disc331 is fixed to a fixed shaft 11 which is united to a casing 313. Thecenter of an upper lid 33 of the casing 313 is provided with a shafthole. To the shaft hole, a driving shaft 322 is vertically movablyfitted. To the bottom of the driving shaft 322 is fixed a driving disc332. The driving disc 332 and the lower fixed disc 331 are connectedwith shape-memory alloy lines 312. To the shape-memory alloy lines 312,a pulse current can be applied from the outside of the casing.

Referring to FIG. 31, the upper fixed disc 334 is fixed to the drivingshaft 322 at its higher part than the upper lid. Between the upper fixeddisc 334 and the upper lid, a spring 324 is provided so that the drivingshaft 322 is pulled up. By virtue of the spring 324, the shape-memoryalloy lines 312 are strained. On the inner surface of the wall of thecasing 313, plural electrodes 320 are arranged vertically. The pluralelectrodes 320 can be arranged so that they become positive electrodeand negative electrode alternately when a voltage is applied. The casingis filled with an electro-sensitive movable fluid 314.

When a voltage is applied to the electrodes 320 of the piston drivingapparatus having the above structure, a jet flow of theelectro-sensitive movable fluid 314 in the circumferential direction ofthe casing 313 is formed in the casing 313. The jet flow of the fluid314 produced by the plural electrodes 320 comes into contact with theshape-memory alloy lines 312. In this stage, the temperature of theshape-memory alloy lines 312 is equal to or lower than the temperatureof the electro-sensitive movable fluid 314.

Then, a pulse current is applied to the shape-memory alloy lines 312,whereby the shape-memory alloy lines 12 generate heat because of theirelectric resistance. When the shape-memory alloy lines 312 reach a giventemperature (said given temperature varies according to the shape-memoryalloy), the memorized shape appears and the shape-memory alloy lines 312are contracted to pull down the upper driving disc 332. If theapplication of a current to the shape-memory alloy lines 312 is stopped,heat generation of the shape-memory alloy lines 312 is also stopped.When the shape-memory alloy lines 312 are cooled to a given temperature,the driving disc 332 is pulled up to the former position by the spring324. The time of applying a current to raise the temperature of theshape-memory alloy lines 312 is relatively short (usually 0.05 to 0.2second), and the driving speed of the piston driving apparatus dependson the cooling rate of the shape-memory alloy lines 312.

When the jet flow of the electro-sensitive movable fluid 314 produced bythe micropump of the invention is brought into contact with theshape-memory alloy lines 312 (targets of cooling), the alloy lines 312can be forcibly cooled. The jet flow, which is produced by the micropumpupon application of a voltage between plural electrodes verticallyprovided on the inner surface of the casing 313, is a flow in thecircumferential direction of the casing 313. The heat energy of the jetflow is transferred to the casing 313 by the contact of the jet flowwith the inner wall surface of the casing 313 and then released outside.

When the shape-memory alloy lines are cooled using the micropump of theinvention as described above, the driving disc 332 can be verticallymoved at a high speed and the amplitude of the driving disc 332 becomeslarge.

In FIG. 31, a rotational flow of the electro-sensitive movable fluid 314in the circumferential direction of the casing 313 is produced by themicropump having plural electrodes 20 which are vertically arranged inthe electro-sensitive movable fluid. However, a jet flow of theelectro-sensitive movable fluid 314 in the vertical direction of thecasing 313 can be produced by providing the electrodes 320 in pluralsteps in the transverse direction of the casing 313, as shown in FIG.32.

Referring to FIG. 32, the piston driving apparatus includes a fixedshaft 311, shape-memory alloy lines 312, a casing 313, anelectro-sensitive movable fluid 314, electrodes 320, a driving shaft322, a spring 324, a driving disc 332, an upper lid 333 and an upperfixed disc 334. The piston driving apparatus shown in FIG. 32 isdifferent from the piston driving apparatus shown in FIG. 31 in thearrangement of the electrodes 320. In the piston driving apparatushaving a micropump wherein the electrodes 320 are arranged at the upperand the lower positions in the electro-sensitive movable fluid 314, theelectro-sensitive movable fluid 314 is convected vertically in thecasing 313, as shown in FIG. 32. The heat from the shape-memory alloylines 12 presumably causes convection of the electro-sensitive movablefluid, though it is slight. By virtue of the arrangement of theelectrodes 20 shown in FIG. 32, more efficient forced cooling may becarried out.

Each of FIG. 31 and FIG. 32 shows an embodiment of the piston drivingapparatus using a micropump wherein plural linear electrodes 320 arearranged in the electro-sensitive movable fluid. Instead of themicropump of this type, micropumps using the aforesaid variouselectrodes are available to perform cooling. In the above embodiments,the voltage applied between the electrodes 320 and the current appliedto the shape-memory alloy lines 312 are separately controlled, but thevoltage applied between the electrodes 320 can be made a pulse voltageby electrically connecting the shape-memory alloy lines 312 to theelectrodes 320. In the case where the pulse voltage is applied betweenthe electrodes 320 to produce a jet flow of the electro-sensitivemovable fluid, the electro-sensitive movable fluid continues to movebecause of the inertia force of the jet flow even when no voltage isapplied. In this case, only one voltage modulation circuit (not shown)is enough, and this contributes to miniaturization of the wholeapparatus and decrease of costs.

The micropump of the invention can be effectively used as a coolingmeans as described above, and hence it can be used as a means to coolshape-memory alloy lines of an actuator wherein a bellows or the like iscontracted by the shape-memory alloy lines.

FIG. 33 schematically shows an embodiment of the microactuator of theinvention.

In FIG. 33(A), a bellows 341 (expansion pump chamber) is expanded. InFIG. 33(B), a bellows 341 (expansion pump chamber) is contracted bymeans of shape-memory alloy lines 312. FIG. 33(C) is a sectional viewtaken on line A—A of FIG. 33(A).

As shown in FIG. 33, the microactuator of the invention includes aninside cylinder (pump chamber) constituted of a bellows 341 and a casing313 provided outside the inside cylinder. A substrate 318 located at thelower end of the bellows 341 (pump chamber) is provided with a suctionvalve 345 and a discharge valve 346. Through the suction valve 345, aliquid can be suctioned from the outside into the bellows 341 (pumpchamber) when the bellows 341 having been contacted is expanded, asshown in FIG. 33(A). From the discharge valve 346, the liquid can bedischarged from the bellows 341 (pump chamber) to the outside when thebellows 341 having been expanded is contracted, as shown in FIG. 33(B).

The pump chamber can be formed from a piston, a bellows or the like. Thebellows is preferably used because the actuator can be made small. Apreferred embodiment using a bellows as the pump chamber is describedbelow.

Between an upper end 317 of the bellows 341 and a lower end of thecasing 313, plural shape-memory alloy lines 312 are stretched. Theshade-memory alloy lines 312 are connected to a controller (not shown)provided outside the microactuator.

The space between the bellows 341 and the casing 313 is filled with theelectro-sensitive movable fluid 314. The electro-sensitive movable fluid314 is usually adjusted to have a temperature lower by 20 to 30° C. thanthe temperature at which the memorized shape of the shape-memory alloylines 312 appears. On the inner surface of the casing 313, pluralelectrodes 320 are provided. The electrodes 320 are generally arrangedin such a manner that they become positive electrode and negativeelectrode alternately. The electrodes 320 are connected to a controller(not shown) provided outside the microactuator.

Between the electrodes 320, a direct-current-voltage controlled by thecontroller is applied. When the voltage is applied between theelectrodes 320, a jet flow of the electro-sensitive movable fluid 314 isproduced in the circumferential direction of the casing 313.

An upper end 319 of the casing 313 is made of an elastic material sothat no negative pressure is applied to the bellows 341 duringcontraction of the bellows 341.

When a current is applied to the shape-memory alloy lines 312 of themicroactuator having the above structure, the shape-memory alloy lines312 generate heat because of their electric resistance and are changedin their shapes. The shape-memory alloy lines 312 used herein arepreferably those having such properties that, when a pulse current isapplied thereto, they have a temperature of 65 to 200° C. and arechanged in their shapes. The power supplied to the shape-memory alloylines of the microactuator of the invention is in the range of usually0.1 to 10 W, though it varies depending on the size of themicroactuator.

When a current is applied to the shape-memory alloy lines 312, theshape-memory alloy lines 312 generate heat because of their electricresistance. By virtue of the heat generation, the shape-memory alloylines 312 are contracted to thereby contract the bellows 341, as shownin FIG. 33(B). With the contraction of the bellows 341, a liquid in thepump chamber (bellows) pushes down the discharge valve and the liquid isdischarged.

A current is applied to the shape-memory alloy lines 312 to contract thebellows 341 as described above, while a voltage is applied between theelectrodes 320 to produce a jet flow of the electro-sensitive movablefluid 314, as shown in FIG. 33(C). The jet flow comes into contact withthe shape-memory alloy lines 312 to lower the temperature of theshape-memory alloy lines 312 to a temperature not higher than thetemperature at which change of shape takes place. The bellows 341 ismade of an elastic material, and when the bellows is liberated from thetension given by the shape-memory alloy lines 312, it returns to theexpanded state shown in FIG. 33(A) from the contracted state shown inFIG. 33(B). With the expansion of the bellows, the suction valve 345 ispushed up, whereby a liquid present outside is suctioned into thebellows 341. That is, application of a current to the shape-memory alloylines and cooling of the shape-memory alloy lines cause contraction andexpansion of the bellows 341, and by virtue of the contraction andexpansion of the bellows, the liquid is suctioned and discharged.

When the jet flow of the electro-sensitive movable fluid 314, which isproduced by the micropump incorporated in the actuator and constitutedof the electrodes 320 and the electro-sensitive movable fluid 314, isused to cool the shape-memory alloy lines 312, the shape-memory alloylines 312 can be forcibly cooled efficiently. That is, the time ofapplying a current to contract the shape-memory alloy lines 312 isusually about 0.05 to 0.2 second and is relatively short. In case ofspontaneous cooling, however, the time required for cooling theshape-memory alloy lines 312 which have once generated heat isconsiderably long. Therefore, if the shape-memory alloy lines 312 areefficiently cooled using the micropump of the invention, the actuator ofthe invention can be driven at a high speed. Besides, the bellows 341can be greatly expanded and contracted, and hence the amount of theliquid which is suctioned or discharged by expansion or contraction atone time can be increased.

The heat transferred to the electro-sensitive movable fluid from theshape-memory alloy lines is released from the surface of the casinghaving a large surface area. Therefore, the temperature of theelectro-sensitive movable fluid is not substantially raised.

For producing a jet flow of the electro-sensitive movable fluid so as toforcibly cool the shape-memory alloy lines 312, a direct-current-voltageof usually 50 V to 30 kV, preferably 100 V to 15 kV, is applied betweenthe electrodes 320. Though a continuous voltage such as adirect-current-voltage is generally applied between the electrodes 320,a discontinuous voltage such as pulse voltage is also available. Even ifthe voltage applied between the electrodes 320 is discontinuous, acontinuous jet flow of the electro-sensitive movable fluid is producedbecause of the inertia force.

As shown in FIG. 33, when a voltage is applied between plural electrodes320 which are vertically arranged on the inner surface of the casing313, the electro-sensitive movable fluid flows in the circumferentialdirection of the casing 313. The flow of the electro-sensitive movablefluid comes into contact with the shape-memory alloy lines 312 (targetsof cooling), whereby the shape-memory alloy lines 312 can be forciblycooled.

In the microactuator of the invention, a current is applied to theshape-memory alloy lines to allow them to generate heat so as to makethem in the desired shape, whereby the bellows is contracted, while theshape-memory alloy lines are brought into contact with the jet flow ofthe electro-sensitive movable fluid to cool the alloy lines. However,the microactuator can be variously modified.

For example, a jet flow of the electro-sensitive movable fluid in thevertical direction of the casing 313 can be produced by arranging theelectrodes as shown in FIG. 32.

The microactuator described above is designed so that the shape-memoryalloy lines generate heat and are contracted to thereby contract thebellows, however, the microactuator may be designed so that theshape-memory alloy lines generate heat and are expanded to thereby drivethe bellows. The bellows may be formed from a shape-memory alloy.

In the microactuator of the invention, the outer surface of the casingcan be provided with a radiating means to increase the radiation area.

In the microactuator of the invention, a voltage is applied to theelectro-sensitive movable fluid to produce a jet flow of the movablefluid. By virtue of the jet flow, the shape-memory alloy lines (targetsof cooling) are cooled to drive the microactuator at a high speed. Themicroactuator of the invention is extremely small. For example, themicroactuator has a diameter of not more than 20 mm and a height of notmore than 30 mm, and preferably has a diameter of not more than 10 mmand a height of not more than 10 mm. In spite of such a small-sizedmicroactuator, the flow rate of the liquid discharged is usually notless than 5 mm³/s, preferably not less than 50 mm³/s, and themicroactuator can be efficiently driven at a remarkably high speed.

Next, the method of controlling relative flow properties of a fluidaccording to the invention and the apparatus used in the method aredescribed in detail.

FIG. 39 schematically shows an embodiment of an apparatus forcontrolling flow, properties of a fluid, which is employable in themethod of the invention.

The control apparatus 410 used in the invention has at least one pair ofelectrodes 412, 414. The pair of electrodes 412, 414 is designed so thatan ununiform electric field can be formed in a fluid 416. If a voltageis applied between a pair of electrodes with smooth surfaces placed in afluid, a uniform electric field is formed in the fluid, and in case ofsuch electrodes, it is difficult to produce a jet flow of a fluid. Inthe present invention, at least one electrode out of the pair ofelectrodes 412, 414 facing each other is an uneven surface electrodehaving a non-smooth surface. Referring to FIG. 39, the upper electrode412 is an uneven surface electrode whose surface is flocked with afibrous material 418. Examples of the uneven surface electrodes includethe above-mentioned flocked electrode, an electrode obtained byproviding a number of metal poles on a surface of an electrodesubstrate, an electrode obtained by forming protrusions and depressionson a surface of an electrode material through embossing or the like, anelectrode obtained by providing protrusions and depressions on a surfaceof an electrode substrate utilizing printing technique or the like, anelectrode of an island structure having depressed sea portion andprotruded island portion, and a honeycomb electrode. Of these, theflocked electrode is preferable. The electrodes capable of forming anununiform electric field in a fluid are sometimes referred to as“flocked electrodes” generically hereinafter. In the flocked electrodes,fibers of the fibrous material are not swayed in a flow formed by ashear stress-generating plate. Therefore, it is different from the caseof the prior art electrode provided with the woven fabric that the shearstress produced by the invention has hydrodynamic continuity, is freefrom yield stress which indicates solidification, and exhibits ease ofcontrolling.

FIG. 39 shows electrodes comprising a pair of circular plates 412, 414each having a diameter of 35 mm. The surface of the upper circular plate412, said surface facing the lower circular plate, is flocked withsynthetic fibers 418. The upper circular plate 412 is rotatably arrangedabove the lower plate 414. Numeral 422 designates a motor to rotate theupper electrode 412. The upper circular plate 412 and the lower circularplate 414 are arranged at a distance of 1.5 mm. The length of the fiberof the fibrous material 418 is 1 mm, and therefore, the distance betweenthe tip of the fiber of the fibrous material 418 and the lower circularplate 414 is 0.5 mm. The upper circular plate 412 is electricallyinsulated from the lower circular plate 414. In FIG. 1, a rotating shaft426 of the motor 422 is provided with a rotational contact point so thata voltage can be applied between the upper circular plate 412 and thelower circular plate 414. The voltage is controlled by a controller 424.

The upper circular plate 412 is connected to the motor 422 (drivingdevice) through the rotating shaft 426. The rotating shaft 426 isprovided with a measuring equipment (not shown) to measure shear stresswhen the upper circular plate is rotated.

The flocked electrode preferably used as the uneven surface electrode inthe invention is an electrode wherein a surface of a metallic substrateis flocked with a fibrous material.

As the fibrous material used for flocking the lower surface of the uppercircular plate shown in FIG. 39, an organic fibrous material, aninorganic fibrous material or a metallic fibrous material can be used.Examples of the organic fibrous materials include chemical fibers, suchas polyamide fibers (nylon fibers), polyester fibers, acrylic fibers,rayon fibers, acetate fibers, vinylon fibers, polypropylene fibers andpolyvinyl chloride fibers; natural fibers, such as cotton fibers, linenfibers and wool fibers; and whiskers of organic materials. Examples ofthe inorganic fibrous materials include glass fibers, asbestos fibersand whiskers of inorganic materials. Examples of the metallic fibrousmaterials include stainless steel fibers, copper fibers, nickel fibers,metallic whiskers, and whiskers of metallic compounds or metallicderivatives such as metallic oxides, metallic nitrides and metalliccarbides. These fibrous materials can be used singly or in combination.

The length of the fibrous material 418 (length of fiber) can beappropriately determined according to the distance between theelectrodes. The length is in the range of usually 1/100 to 95/100,preferably 1/100 to 80/100, more preferably 1/100, to 80/100, of thedistance between the electrodes. For example, in the apparatus 410 shownin FIG. 39, the distance between the upper circular plate 412 and thelower circular plate 414 is 1.5 mm, and the length of the fibrousmaterial 18 provided on the upper circular plate is 1.0 mm. The finenessof the fibrous material 418 is in the range of usually 0.5 to 20deniers, preferably 1.0 to 5.0 deniers. If the fineness of the fibrousmaterial greatly deviates from this range, uniform flocking of thesurface of the electrode material with the fibrous material becomesdifficult, and the resulting flocked electrode shows scattered shearstress values. Further, dense flocking with the fibrous material maycause scattering of the shear stress values, because the dense area hashigh resistance to the fluid even when no voltage is applied andinevitably a difference of the resistance from the state of voltageapplication becomes small, though it depends on the flocking density(number of fibers per unit area).

The number of fibers of the fibrous material can be appropriatelydetermined in consideration of the flow properties of the fluid to becontrolled, and is in the range of usually 1,000 to 50,000 per 1 cm²,preferably 3,000 to 30,000 per 1 cm². The total area of the sections ofthe fibers is usually 1 to 75%, preferably 5 to 35%, based on the areaof the electrode surface having the fibers thereon. In the method of theinvention, a jet flow of the fluid is produced between the tip of thefibrous material (tip of the flocked electrode) and the other electrode.Therefore, if the flocking density of the fibrous material is low, a jetflow is produced on a small scale. That is, when the flocking density islow, the jet flow produced upon application of a voltage is too small tosufficiently control the flow properties of the fluid. On the otherhand, flocking with a larger number of fibers than the above range ispractically impossible from the industrial viewpoint.

There is no specific limitation on the process for flocking theelectrode material (substrate) with the fibrous material. For example,the ends of the fibers are bonded to a surface of the electrode materialsuch as a metal through an adhesive (flocking glue) layer 428, or theends of the fibers are fusion bonded to the surface of the electrodematerial. If the fibrous material is a metal or an inorganic material,the metal or the inorganic material may be allowed to grow in the formof fibers on the surface of the electrode material.

The other electrode 414, which faces the flocked electrode having thefibrous material 418 thereon, can be formed from any of variousmaterials, with the proviso that a voltage can be applied between theelectrodes. Examples of the materials for forming the electrode 414include metals, carbon materials such as graphite, conductive metallicoxides, coating materials capable of forming a conductive layer, andconductive films. The surfaces of these electrode-forming materials maybe covered with cloth or the like. In FIG. 39, the electrode 414 isformed from a metal.

The gap between the flocked electrode 12 and the other electrode 414 isfilled with a fluid 16 which is substantially dielectric at its workingtemperature. FIG. 39 shows an embodiment wherein the flocked electrode12 and the other electrode 414 are immersed in a fluid contained in acontainer 430. By immersing the flocked electrode 412 and the otherelectrode 414 in the fluid 16 contained in the container 430, the gapbetween the flocked electrode 412 and the other electrode 414 is filledwith the fluid.

The fluid 416 filled in the gap between the flocked electrode 412 andthe other electrode 414 is a fluid which shows flowability at itsworking temperature. In the invention, the fluid 416 is preferably afluid which is substantially dielectric at its working temperature. Bythe expression “fluid which is substantially dielectric” is meant thatthe fluid has a conductivity (σ) of usually not more than 1×10⁻⁶ S·m⁻¹,preferably not more than 2.5×10⁻⁶ S·m⁻¹. Examples of the fluids includesilicone oil, hydraulic oil, transformer oil, lubricating oil, mineraloil, cutting oil and bearing oil. The dielectric fluid preferably hasconductivity and viscosity equivalent to those of the aforesaidelectro-sensitive movable fluid.

A voltage is applied between the flocked electrode 412 and the otherelectrode 414 between which the substantially dielectric fluid 416 isheld. The applied voltage is, for example, rectangular voltage, pulsevoltage or continuous voltage. The intensity of the applied voltage isin the range of usually 10 V to 10 kV, preferably 50 V to 6 kV. Even ifthe fluid to which a voltage is applied is substantially dielectric, acurrent is produced in the fluid, though it is very small. The currentis usually 0.001 to 100 μA/cm², in many cases 0.05 to 20 μA/cm², thoughit varies depending on the type of the fluid, the type of the flockedelectrode and the distance between the electrodes.

When a voltage is applied between the electrodes as described above, ajet flow of the fluid is produced between the tip of the fibrousmaterial 418 of the flocked electrode 412 (uneven surface electrode) andthe other electrode. That is, by the use of the uneven surfaceelectrode, an ununiform electric field is formed in the fluid filled inthe gap between the electrodes, and by virtue of the ununiform electricfield, a jet flow of the fluid is produced. When the flocked electrodeis used, a jet flow is produced between the tip of each fiber and theother electrode, and the jet flow often becomes a circulating flow. Forexample, in FIG. 39, plural circulating flows are produced in thevertical direction between the flocked electrode 12 and the otherelectrode 414. The circulating flows thus produced are almostperpendicular to the fluid which moves horizontally between theelectrodes, and therefore the circulating flows function as shear stressagainst the fluid which moves horizontally between the electrodes. Theflow rates (or intensities) of the circulating flows can be controlledby the intensity of the voltage applied between the flocked electrodeand the other electrode. In FIG. 39, the flow properties of the fluidwhich moves horizontally can be controlled by varying the voltageapplied between the flocked electrode 412 and the other electrode 414.

FIG. 40 shows change in a viscosity of a dielectric hydraulic oil(silicone oil) given when the upper circular plate (flocked electrode)is rotated with applying a voltage of 0.25 to 2 kV between the flockedelectrode and the other electrode arranged in such a manner that thedistance between the tip of the fibrous material of the flockedelectrode and the other electrode is made 0.5 mm and the silicone oil isfilled in the gap between those electrodes. For comparison, a viscosityof the hydraulic oil given when no voltage is applied is also shown inFIG. 40.

It is generally known as the electrical rheology effect that theviscosity of a fluid varies when a voltage is applied to the fluid. Thisresults from change of state of the fluid caused by the electric field.For example, as for the particle dispersion type electro-rheologicalfluids, it is understood that the particles undergo dielectricpolarization owing to the electric field to form a chain structurebetween the electrodes, whereby shear stress of the fluid is increased.As a result, the viscosity of the fluid is increased. As for the liquidcrystals which are homogeneous electro-rheological fluids, it isunderstood that molecules of the crystal material are orientated in onedirection owing to the electric field, whereby shear stress of the fluidis increased. As a result, the viscosity of the fluid is increased.

The silicone oil used in the control method of the invention is,however, electrically stable and does not have such orientationproperties as of the particle dispersion type fluids or the crystals, sothat it is impossible that a chain structure is formed as in theheterogeneous fluids or the molecules are orientated as in the crystals.The silicone oil is known to exhibit stable state in the electric field,and for this reason, the silicone oil is widely used now as an excellentdielectric fluid.

According to the invention, even if the electrically stable silicone oilis used, a jet flow (circulating flow in many cases) of the fluid(silicone oil) is observed between the tip of the fibrous material ofthe flocked electrode and the other electrode upon application of avoltage between the electrodes. By virtue of the jet flow, shear stressof the silicone oil is increased, and the flow properties of thesilicone oil can be controlled by the voltage applied between theelectrodes. This behavior is not limited to the silicone oil, and othercommon hydraulic oils also exhibit similar behavior.

The jet flow (particularly circulating flow) of the fluid thus producedfunctions as shear stress against a motion of the fluid which crosses atright angles to the direction of voltage application.

According to the invention, therefore, the flow properties of the fluidagainst the flocked electrode can be easily controlled by application ofa voltage between the electrodes. Moreover, the control of the flowproperties can be extremely precisely carried out by controlling thevoltage applied between the electrodes.

In the invention, further, the flow properties can be controlled byusing an ordinary dielectric fluid as it is, without adding particles orthe like, and by incorporating the electrodes into the existing device.Therefore, alteration of equipment on a large scale is unnecessary. Inthe invention, the electrodes can be moved or can be fixed as shown inFIG. 39. When a fluid is allowed to flow between the fixed electrodesand a voltage is applied therebetween, the flow properties of the fluidwhich passes between the fixed electrodes can be controlled. That is,relative flow properties of the fluid to the electrodes can becontrolled by the method of the invention.

The control method of the invention can be widely applied to variousindustries, and can be made to serve as a hydraulic valve having noslide member and controllable by a voltage in the hydraulic mechanismusing ordinary hydraulic oil. Further, the control method of theinvention can be applied to automobile parts such as clutch and shockabsorber, industrial machine parts and vibration-damping mechanism.

The method of controlling flow properties of a fluid according to theinvention is to control flow properties of a fluid by applying a voltageto a dielectric fluid through uneven surface electrode, as describedabove, but this method can be variously modified.

For example, various additives, such as antioxidant, stabilizer,colorant, anti-corrosive agent, viscosity modifier, antiseptic agent,mildew-proofing agent, solvent, flowability adjusting agent and surfaceactive agent, can be added to the fluid employable in the invention,though addition of those components is not always necessary.

EFFECT OF THE INVENTION

The micromotor of the invention is extremely small, and the thinmicromotor of the invention is extremely thin. In spite of the small orthin micromotor, it can be driven at a high rotational speed of severalhundreds to several tens of thousands rpm. The micromotor of theinvention hardly generates heat even when it rotates at a high speed.

The micromotor and the linear motor of the invention utilize jet flow ofan electro-sensitive movable fluid produced in an electric field, butnot magnetic force or magnetic field, and therefore they are normallydriven even in a strong magnetic field and generate none of magnetism,driving noise and electromagnetic noise.

The linear motor of the invention is driven by such an entirely newmechanism that a direct-current-voltage is applied in such a manner thatan ununiform electric field is formed in a specific electro-sensitivemovable fluid. The linear motor can be more efficiently driven by makingthe size smaller, and the linear motor hardly generates heat.

There is also provided by the invention a micropump of an entirely newmechanism comprising a specific electro-sensitive movable fluid andelectrodes. This micropump is driven by applying a voltage to theelectro-sensitive movable fluid and does not have such a driving meansas used in the conventional pumps. Therefore, the micropump can beeasily miniaturized and can be easily incorporated in the conventionalmicroactuators and pumps. Further, since the micropump uses no magneticforce as the driving force, it can be driven even in a strong magneticfield.

The micropump of the invention can be used as a circulating pump, atransfer pump or a jet pump of an electro-sensitive movable fluid. Bybringing the jet flow of the electro-sensitive movable fluid produced bythe micropump into contact with the target, heat energy exchange betweenthe target and the electro-sensitive movable fluid can be carried out.For example, when the temperature of the target is higher than that ofthe electro-sensitive movable fluid, the micropump can be used as ameans to cool the target. When the micropump of the invention isincorporated in a microactuator using a shape-memory alloy as a drivingsource, this micropump can be used as a means to cool the shape-memoryalloy. Since the microactuator of the invention uses no electromagneticmotor, it can be favorably driven even in a strong magnetic field.

The micropump of the invention can be incorporated in a small-sizedapparatus wherein a conventional micropump using an electromagneticmotor cannot be incorporated. Moreover, since the micropump of theinvention does not have any driving means which easily causes troubles,it can be used continuously for a long period of time.

In the method of controlling flow properties of a fluid according to theinvention, flow properties of a substantially dielectric fluid can becontrolled by the use of a flocked electrode. Since it is unnecessary toadd particles or the like to the fluid employable in the invention,sedimentation or flotation of particles does not take place. Further,since a conventional dielectric fluid is available, the method iseconomically advantageous. Furthermore, the shear stress produced by theinvention has hydrodynamic continuity, is free from yield stress whichindicates solidification and has ease of controlling, so that theapparatus used in the method can be simplified.

EXAMPLE

The present invention is further described with reference to thefollowing examples, but it should be construed that the invention is inno way limited to those examples.

Example 1

A SE type ECF motor having a structure shown in FIG. 2(A) wasfabricated. That is, as a fluid container of the SE type ECF motor, acylinder having an inner diameter of 16 mm and a depth of 3.5 mm wasused. The bottom surface of the cylinder and the lower surface of a lideach was provided with four pairs of electrodes in such a manner thatthe angle between a pair of electrodes (positive electrode and negativeelectrode) was 22.5° and the angle between the adjacent positiveelectrodes was 90°.

A circular film having a rotating shaft at its center and having adiameter of 15 mm was used as a rotator. As the flow receiving members,8 convex bars each having a section of right-angled triangle wereattached to the upper surface of the circular film, and 8 convex barshaving the same section as above were attached to the lower surface ofthe circular film (total number of bars: 16).

The fluid container was filled with 16 ml of dibutyl decanedioate (DBD).

Then, a direct-current-voltage of 6.0 kV was applied between theelectrodes of the thus fabricated SE type ECF motor. As a result, therotator of the SE type ECF motor underwent steady rotation at 510 rpm,and the rotator (SE type ECF motor) continued to rotate stably duringthe application of a voltage. The intensity of the current in DBD was2.0 μA, and the rotational direction was the same as the flow directionof DBD (i.e., direction of the positive electrode to the negativeelectrode). When the polarities of the electrodes between which thevoltage was applied were reversed, the rotator 30 rotated at the samerotational speed in the opposite direction, and the intensity of thecurrent was the same as above.

Example 2

The SE type ECF motor was driven in the same manner as in Example 1,except that the rotator having a flow receiving member consisting of 16convex bars was replaced with a rotator having a flow receiving memberconsisting of 8 convex bars (4 convex bars each having a section ofright-angled triangle attached to the upper surface and 4 convex barshaving the same section attached on the lower surface). As a result, theSE type ECF motor underwent steady rotation at 340 rpm, and therotational direction was the same as in Example 1.

Example 3

The SE type ECF motor was driven in the same manner as in Example 1,except that linalyl acetate was used in place of the dibutyldecanedioate (DBD). As a result, the SE type ECF motor underwent steadyrotation at 740 rpm, the intensity of the current was 1.8 μA, and therotational direction was the same as the flow direction of the linalylacetate (i.e., direction of the positive electrode to the negativeelectrode).

Example 4

The SE type ECF motor was driven in the same manner as in Example 1,except that dibutyl dodecanedioate was used in place of the dibutyldecanedioate (DBD). As a result, the SE type ECF motor underwent steadyrotation at 480 rpm, the intensity of the current was 1.8 μA, and therotational direction was the same as the flow direction of the dibutyldodecanedioate (i.e., direction of the positive electrode to thenegative electrode).

Example 5

An engineering plastic (insulating material) was cut to prepare arotator having a diameter of 19 mm and a thickness of 1.0 mm. Therotator had at its center a rotating shaft (diameter: 1.0 mm) united tothe rotator in one body.

The united product of the rotator and the rotating shaft was providedwith electrodes by means of electroless nickel plating, as shown in FIG.5. The electrodes had a thickness of 5 μm.

The united product consisting of the rotator and the rotating shaft andprovided with the electrodes was incorporated in a housing having aninner diameter of 22 mm and a depth of 4 mm, as shown in FIG. 4(A), andthe housing was filled with 1 ml of dibutyl decanedioate (DBD).

Then, a direct-current-voltage of 6.0 kv was applied between theelectrodes of the thus fabricated RE type ECF motor. As a result, therotator of the RE type ECF motor underwent steady rotation at 320 rpm,and the rotator (RE type ECF motor) continued to rotate stably duringthe application of a voltage. The, itensity of the current in DBD was1.5 μA, and the rotational direction was a direction of the reaction ofthe jet flow produced between the electrodes provided on the rotator.When the polarities of the electrodes between which the voltage wasapplied were reversed, the rotator rotated at the same rotational speedin the opposite direction, and the intensity of the current was the sameas the above.

Example 6

The RE type ECF motor was driven in the same manner as in Example 5,except that linalyl acetate was used in place of the dibutyldecanedioate (DBD). As a result, the RE type ECF motor underwent steadyrotation at 440 rpm, and the intensity of the current was 1.4 μA.

Example 7

The RE type ECF motor was driven in the same manner as in Example 5,except that dibutyl dodecanedioate was used in place of the dibutyldecanedioate (DBD). As a result, the RE-type ECF motor underwent steadyrotation at 300 rpm, and the intensity of the current was 1.5 μA.

Example 8

Using the SE type ECF motor shown in FIG. 9 and FIG. 10, propertiesgiven when the size of the motor was made smaller were examined. The SEtype ECF motor used herein was one having a medium container 211 (innerdiameter: 4 mm) made of an engineering plastic and a vane rotor 230 with8 vanes made of a polyester film (thickness: 0.5 mm). This SE type ECFmotor is referred to as “4 mm SE type ECF motor” hereinafter. In thebearing section of the 4 mm SE type ECF motor, a bearing means wasincorporated. As the electro-sensitive movable fluid, dibutyldecanedioate (DBD) was used. FIG. 19 shows a relation between appliedvoltage, rotational speed and current in the 4 mm SE type ECF motor.

Separately, a SE type ECF motor having the same structure as that of the4 mm SE type ECF motor but having a double size (inner diameter of fluidcontainer: 8 mm) was prepared. This SE type ECF motor is referred to as“8 mm SE type ECF motor” hereinafter. As the electro-sensitive movablefluid, dibutyl decanedioate (DBD) was used.

A direct-current-voltage of 0 to 6 kV was applied to each of the 4 mm SEtype ECF motor and the 8 mm SE type ECF motor, to measure rotationalspeed, input power and output power of the SE type ECF motors at eachvoltage. From the input power and the output power, the efficiency(output power/input power) of the 4 mm SE type ECF motor and the 8 mm SEtype ECF motor was calculated. The results are shown in FIG. 18. FIG.18(A) shows the rotational speed, input power, output power andefficiency of the 4 mm SE type ECF motor. FIG. 18(B) shows therotational speed, input power, output power and efficiency of the 8 mmSE type ECF motor. The input power was determined by the applied voltageand the current, and the output power was determined by the torque andthe number of rotations.

As is clear from FIG. 18(A), the maximum value of the efficiency of the4 mm SE type ECF motor was 17% at an applied voltage of 2 kV. On theother hand, the maximum value of the efficiency of the 8 mm SE type ECFmotor was about 1.7%. That is, the efficiency of the micromotor of theinvention became 10 times by reducing the diameter of the micromotor to½ of the initial diameter.

Then, the maximum output power density of the 4 mm SE type ECF motor andthat of the 8 mm SE type ECF motor were determined. The 4 mm SE type ECFmotor had a motor volume (sectional area of motor at its innerdiameter×length of rotor) of 7.5×10⁻⁸ m³, so that the maximum outputpower density of the 4 mm SE type ECF motor became 2.6×10³ W/m³. The 8mm SE type ECF motor had a motor volume of 7×10⁻⁷ m³, so that themaximum output power density 8 mm SE type ECF motor became 4×10² W/m³.Therefore, the 4 mm SE type ECF motor was confirmed to have an outputpower density of about 7 times as much as the 8 mm SE type ECF motor.

Further, the efficiency was measured in the same manner as above, exceptthat linalyl acetate (electro-sensitive movable fluid) was filled in the4 mm SE type ECF motor in place of the dibutyl decanedioate (DBD). As aresult, it was confirmed that the maximum efficiency reached about 40%.

The driving of the SE type ECF motor mentioned above is one embodimentof the driving of the micromotor according to the invention, and otherthan the SE type ECF motor, various motors such as RE type ECF motor andcup type ECF motor can be driven similarly to the above. Even when othermicromotors are driven, the same tendency as in the SE type ECF motorcan be obtained.

Example 9

A SE type ECF linear motor having a structure shown in FIG. 20 wasfabricated. That is, between an outer cylinder having an inner diameterof 25 mm and a length of 38 mm and an inner cylinder having an outerdiameter of 16 mm and a length of 35 mm, a pair of coil electrodes wasarranged in such a manner that the coil electrodes were wound 4 timesaround the inner cylinder and that an ununiform electric field wasformed in the electro-sensitive movable fluid. In other words, the pairof electrodes was arranged so that the distance between an electrode andits one adjacent electrode was 2 mm and the distance between theelectrode and the other adjacent electrode was 4 mm and that anununiform electric field was formed. In the inner cylinder (innerdiameter: 12 mm), a piston (diameter: 9.7 mm) fixed to the driving shaftwas disposed. Then, the fluid container thus formed was filled withabout 13 ml of linalyl acetate.

When a direct-current-voltage of 9.0 kV was applied between the pair ofcoil electrodes of the SE type ECF linear motor, the piston began tomove. The moving rate of the piston was measured by means of a laserdisplacement sensor meter. The results are shown in FIG. 25.

As is clear from FIG. 25, the piston began to accelerate immediatelyafter application of a voltage, and after about 40 ms, the moving ratereached 0.065 m/s, followed by equilibrium state. The intensity of thecurrent was 2.0 μA. The moving direction of the piston was the same asthe direction of the jet flow of the linalyl acetate produced betweenthe coil electrodes, that is, the direction of the positive electrode tothe negative electrode.

The laser displacement sensor meter used was that of LB series(available from Keyence Co.) using a sensor head of LB-02 and anamplifier of LB-06. The measurement was carried out in the measuringrange of ±10 mm.

If the polarities of the electrodes are reversed in the SE type ECFlinear motor, the piston moves in the opposite direction.

Example 10

The SE type ECF linear motor was driven in the same manner as in Example9, except that dibutyl decanedioate was used in place of the linalylacetate.

As a result, the piston began to accelerate immediately afterapplication of a voltage, and after about 50 ms, the moving rate reached0.47 m/s, followed by equilibrium state. The intensity of the currentwas 2.2 μA. The moving direction of the piston was the same as thedirection of the jet flow of the dibutyl decanedioate produced betweenthe coil electrodes, that is, the direction of the positive electrode tothe negative electrode.

Example 11

The SE type ECF linear motor was driven in the same manner as in Example9, except that dibutyl dodecanedioate was used in place of the linalylacetate.

As a result, the piston began to accelerate immediately afterapplication of a voltage, and after about 50 ms, the moving rate reached0.45 m/s, followed by equilibrium state. The intensity of the currentwas 2.1 μA. The moving direction of the piston was the same as thedirection of the jet flow of the dibutyl dodecanedioate produced betweenthe coil electrodes, that is, the direction of the positive electrode tothe negative electrode.

Example 12

In a cylinder having an inner diameter of 12 mm and a length of 35 mm, adriving shaft equipped with two circular mesh electrode plates eachhaving a diameter of 10 mm was arranged. The two mesh electrode plateshad a mesh size of 1 mm, and they were arranged in such a manner thatthey faced each other at a distance of 2.5 mm and were electricallyinsulated from each other.

The cylinder was filled with about 4 ml of linalyl acetate to prepare aPE Type ECF linear motor. The two circular mesh electrode plates of themotor were set to a positive electrode and a negative electrode, and adirect-current-voltage of 9.0 kV was applied between the electrodes. Thecircular mesh electrode plates began to move toward the positiveelectrode immediately after application of a voltage, and after about 30ms, the moving rate reached 0.38 m/s, followed by equilibrium state. Theintensity of the current was 1.7 μA.

The jet flow of the linalyl acetate was produced in the direction of thepositive electrode to the negative electrode, while the circular meshelectrode plates were moved in the direction of the reaction of the jet.flow (i.e., opposite direction to the direction of the jet flow).

Example 13

The PE type ECF linear motor was driven in the same manner as in Example12, except that dibutyl decanedioate was used in place of the linalylacetate.

As a result, the circular mesh electrode plates began to accelerateimmediately after application of a voltage, and after about 40 ms, themoving rate reached 0.25 m/s, followed by equilibrium state. Theintensity of the current was 2.0 μA. The jet flow of the dibutyldecanedioate was produced in the direction of the positive electrode tothe negative electrode, while the circular mesh electrode plates weremoved in the direction of the reaction of the jet flow (i.e., oppositedirection to the direction of the jet flow).

Example 14

The PE type ECF linear motor was driven in the same manner as in Example12, except that dibutyl dodecanedioate was used in place of the linalylacetate.

As a result, the circular mesh electrode plates began to accelerateimmediately after application of a voltage, and after about 40 ms, themoving rate reached 0.22 m/s, followed by equilibrium state. Theintensity of the current was 2.0 μA. The jet flow of the dibutyldodecanedioate was produced in the direction of the positive electrodeto the negative electrode, while the circular mesh electrode plates weremoved in the direction of the reaction of the jet flow (i.e., oppositedirection to the direction of the jet flow).

Example 15

An apparatus shown in FIG. 31 was fabricated. That is, four pairs (8lines) of shape-memory alloy lines 312 were stretched between a drivingplate 332 and a lower fixed plate 331 in a casing 313 having a diameterof 15 mm. To the driving plate 332, a driving shaft 322 was joined, andthe driving shaft 322 was extended outside from the center of an upperlid 333 of the casing 313. On the inner surface of the casing 313, fourpairs (8 lines) of electrodes 320 were stretched in the verticaldirection. The casing 313 was filled with dibutyl decanedioate (DBD)(σ=1.35×10⁻⁹ S/m, η=7.0×10⁻³ Pa·s) as the electro-sensitive movablefluid 314. The driving shaft 322 was provided with a coil spring havinga spring constant of 1.9 N/mm as the spring 324, and was equipped with alinear potentiometer (not shown) for measuring output displacement(measuring range: 0-1 mm).

The current applied to the shape-memory alloy lines was controlled by apersonal computer, and the output voltage measured by the linearpotentiometer was controlled by the same computer after A/D conversion.The sampling frequency was 1 KHz.

A direct-current-voltage of 3 kV was applied between the electrodes 320of the above apparatus to drive a micropump incorporated in theapparatus and thereby produce a jet flow of the DBD in the casing 313.Then, a pulse current of 0.9 W was applied to the shape-memory alloylines 312, and the amplitude displacement was measured when the steadystate was reached. In this measurement, the pulse width of the pulsecurrent applied to the shape-memory alloy lines was 20 ms, and a statewhere the change of the amplitude displacement became 3% was taken asthe steady state.

The amplitude displacement is shown in FIG. 34.

Further,. the power applied to the shape-memory alloy lines was variedto 0.5 W, 0.7 W, 1.1 W or 1.3 W to measure variation of the amplitude.The results are shown in FIG. 35.

Comparative Example 1

The amplitude displacement was measured in the same manner as in Example15, except that no voltage was applied between the electrodes 320 sothat the micropump was not driven, and the same power was applied to theshape-memory alloy lines.

The result is shown in FIG. 34.

Example 16

The amplitude displacement was measured in the same manner as in Example15, except that the arrangement of the electrodes 320 was varied to thatshown in FIG. 32 so as to produce a jet flow of the DBD in the verticaldirection by means of the micropump.

The result is shown in FIG. 36.

Comparative Example 2

The amplitude displacement was measured in the same manner as in Example16, except that no voltage was applied between the electrodes 320 sothat the micropump was not driven, and the same power was applied to theshape-memory alloy lines.

The result is shown in FIG. 36.

Example 17

A microactuator shown in FIG. 37 was fabricated. That is, a casing 313was placed on a substrate 318, and a pump chamber was formed from abellows 341. The substrate 318 having the bellows 341 thereon wasprovided with a suction valve 345 made of a rubber having a thickness of0.2 mm and a discharge valve 346 made of a rubber having a thickness of0.2 mm. By virtue of expansion and contraction of the bellows 341, afluid (tap water in Example 17) can be made to be suctioned ordischarged. Between the upper end of the bellows 341 and the substrate318, eight shape-memory alloy lines 312 were stretched. The bellows 341is formed from an elastic material, and therefore when a power is notsupplied to the shape-memory alloy lines 312, the shape-memory alloylines are strained because of the elastic recovery of the bellows 341.On the inner surface of the casing 313, eight electrodes 320 wereprovided, and these electrodes 320 were set to positive electrode andnegative electrode alternately. The casing 13 was filled with DBD.

A direct-current-voltage of 3 kV was applied between the electrodes 320to produce a jet flow of DBD (electro-sensitive movable fluid 314) inthe circumferential direction of the casing 313.

Then, a pulse current (pulse width: 20 ms) of 0.5 w was applied to theshape-memory alloy lines 312, to measure the amount (flow rate) of thedischarged tap water by means of a measuring cylinder.

Further, a pulse current (pulse width: 20 ms) of 0.7 W or 0.9 W wasapplied to the shape-memory alloy lines 312, to measure the amount (flowrate) of the discharged tap water in a manner similar to the above.

The results are shown in FIG. 38.

Comparative Example 3

The amount (flow rate) of the discharged water was measured in the samemanner as in Example 17, except that no voltage was applied between theelectrodes 320.

The results are shown in FIG. 38.

Example 18

A circular flat metallic plate having a diameter of 35 mm was coatedwith a flocking glue in a thickness of 0.1 mm, and the glue layer isflocked with rayon fibers having a length of 1.0 mm and a fineness of 3deniers (trade name: Corona, available from Daiwa Spinning Co., Ltd.) inan electric field of 30,000 V by an electrostatic flocking method, toobtain a rayon fiber flocked electrode plate.

The number of fibers per cm² was 8,200.

In a container, the rayon fiber flocked electrode plate was arranged asan upper circular plate of a parallel flat plate type measuring sensor.Below the rayon fiber flocked electrode, a lower electrode was arrangedat a distance of 0.5 mm from the tips of the fibers. Then, the containerwas filled with a silicone oil having a viscosity of 0.1 Pa·s at roomtemperature.

The upper electrode (flocked electrode) arranged as above was rotated toimpart shear rates to the silicone oil, and a direct-current-voltage wasapplied between the flocked electrode (positive electrode) and the lowerelectrode (negative electrode) to measure a viscosity of the siliconeoil at each shear rate and a current in the silicone oil. The resultsare shown in Table 3 and FIG. 40.

TABLE 3 Length of Fineness of Applied fiber fiber voltage Current (mm)(d) (kV) (μA/cm²) 1.0 3 0.25 <0.1 0.5 0.1 1.0 0.3 2.0 1.5

Example 19

A viscosity of the silicone oil at each shear rate and a current in thesilicone oil were measured in the same manner as in Example 1, exceptthat nylon fibers having a length of 1.0 mm and a fineness of 2 deniers(trade name: Toray Nylon, available from Toray Industries, Inc.) wereused in place of the rayon fibers having a length of 1.0 mm and afineness of 3 deniers. The results are shown in Table 4 and FIG. 41.

TABLE 4 Length of Fineness of Applied fiber fiber voltage Current (mm)(d) (kV) (μA/cm²) 1.0 2 1.0 0.1 2.0 0.2

Example 20

A viscosity of the silicone oil at each shear rate and a current in thesilicone oil were measured in the same manner as in Example 18, exceptthat acrylic fibers having a length of 1.0 mm and a fineness of 2deniers (trade name: Kanekalon, available from Kanegafuchi ChemicalIndustry Co., Ltd.) were used in place of the rayon fibers having alength of 1.0 mm and a fineness of 3 deniers. The results are shown inTable 5 and FIG. 42.

TABLE 5 Length of Fineness of Applied fiber fiber voltage Current (mm)(d) (kV) (μA/cm²) 1.0 2 2.0 0.2

Example 21

A viscosity of a hydraulic oil at each shear rate and a current in thehydraulic oil were measured in the same manner as in Example 18, exceptthat a hydraulic oil of ISO viscosity grade 32 (conductivity: 6.0×10⁻¹⁰s/m, viscosity: 5.9×10⁻² Pa-s, trade name: Daphne Super Hydraulic Fluid32, available from Idemitsu Kosan Co., Ltd.) was used in place of thesilicone oil, and the applied voltage was varied to 0 kV, 1.0 kV, 2.0 kVand 3.0 kV. The results are shown in Table 6 and FIG. 43.

Example 22

A viscosity of a hydraulic oil at each shear rate and a current in thehydraulic oil were measured in the same manner as in Example 18, exceptthat nylon fibers having a length of 1.0 mm and a fineness of 2 deniers(trade name: Toray Nylon, available from Toray Industries, Inc.) wereused in place of the rayon fibers, and a hydraulic oil of ISO viscositygrade 32 (conductivity: 6.0×10⁻¹⁰ s/m, viscosity: 5.9×10⁻² Pa·s, tradename: Daphne Super Hydraulic Fluid 32, available from Idemitsu KosanCo., Ltd.) was used in place of the silicone oil. The results are shownin Table 6 and FIG. 44.

Example 23

A viscosity of a hydraulic oil at each shear rate and a current in thehydraulic oil were measured in the same manner as in Example 1, exceptthat acrylic fibers having a length of 1.0 mm and a fineness of 2deniers (trade name: Kanekalon, available from Kanegafuchi ChemicalIndustry Co., Ltd.) were used in place of the rayon fibers, and ahydraulic oil of ISO viscosity grade 32 (conductivity: 6.0×10⁻¹⁰ s/m,viscosity: 5.9×10⁻² Pa·s, trade name: Daphne Super Hydraulic Fluid 32,available from Idemitsu Kosan Co., Ltd.) was used in place of thesilicone oil. The results are shown in Table 6 and FIG. 45.

Example 24

A viscosity of a hydraulic oil at each shear rate and a current in thehydraulic oil were measured in the same manner as in Example 18, exceptthat rayon fibers having a length of 0.3 mm and a fineness of 1.5deniers (trade name: Corona, available from Daiwa Spinning Co., Ltd.)were used in place of the rayon fibers having a length of 1.0 mm and afineness of 3 deniers, and a hydraulic oil of ISO viscosity grade 32(conductivity: 6.0×10⁻¹⁰ s/m, viscosity: 5.9×10⁻² Pa·s, trade name:Daphne Super Hydraulic Fluid 32, available from Idemitsu Kosan Co.,Ltd.) was used in place of the silicone oil. The results are shown inTable 6 and FIG. 46.

Example 25

A viscosity of a hydraulic oil at each shear rate and a current in thehydraulic oil were measured in the same manner as in Example 18, exceptthat vinylon fibers having a length of 0.4 mm and a fineness of 1.5deniers (trade name: Kuraray Vinylon, available from Kuraray Co., Ltd.)were used in place of the rayon fibers, and a hydraulic oil of ISOviscosity grade 32 (conductivity: 6.0×10⁻¹⁰ s/m, viscosity: 5.9×10⁻²Pa·s, trade name: Daphne Super Hydraulic Fluid 32, available fromIdemitsu Kosan Co., Ltd.) was used in place of the silicone oil. Theresults are shown in Table 6 and FIG. 47.

Example 26

A viscosity of a hydraulic oil at each shear rate and a current in thehydraulic oil were measured in the same manner as in Example 18, exceptthat vinylon fibers having a length of 0.2 mm and a fineness of 1.5deniers (trade name: Kuraray Vinylon, available from Kuraray Co., Ltd.)were used in place of the rayon fibers, and a hydraulic oil of ISOviscosity grade 32 (conductivity: 6.0×10⁻¹⁰ s/m, viscosity: 5.9×10⁻²Pa·s, trade name: Daphne Super Hydraulic Fluid 32, available fromIdemitsu Kosan Co., Ltd.) was used in place of the silicone oil. Theresults are shown in Table 6 and FIG. 48.

TABLE 6 Length Fineness Applied Type of of fiber of fiber voltageCurrent fiber (mm) (d) (kV) (μA/cm²) Figure rayon 1.0 3 1.0 0.7 FIG. 43rayon 1.0 3 2.0 2.6 FIG. 43 rayon 1.0 3 3.0 5.2 FIG. 43 nylon 1.0 2 2.01.5 FIG. 44 acrylic 1.0 2 2.0 1.0 FIG. 45 rayon 0.3 1.5 2.0 3.1 FIG. 46vinylon 0.4 1.5 2.0 0.7 FIG. 47 vinylon 0.2 1.5 2.0 0.3 FIG. 48

Example 27

A viscosity of a hydraulic oil at each shear rate and a current in thehydraulic oil were measured in the same manner as in Example 18, exceptthat a hydraulic oil of ISO viscosity grade 100 (trade name: DaphneSuper Hydraulic Fluid 100, available from Idemitsu Kosan Co., Ltd.) wasused in place of the silicone oil. The results are shown in Table 7 andFIG. 49.

Example 28

A viscosity of a hydraulic oil at each shear rate and a current in thehydraulic oil were measured in the same manner as in Example 18, exceptthat a hydraulic oil of ISO viscosity grade 22 (trade name: Daphne SuperHydraulic Fluid 22, available from Idemitsu Kosan Co., Ltd.) was used inplace of the silicone oil. The results are shown in Table 7 and FIG. 50.

TABLE 7 Iso Length of Fineness Applied viscosity fiber of fiber voltageCurrent grade (mm) (d) (kV) (μA/cm²) 100 1.0 3 2.0 0.8  22 1.0 3 2.0 4.2

Example 29

A viscosity of a hydraulic oil at each shear rate and a current in thehydraulic oil; were measured in the same manner as in Example 21, exceptthat the upper electrode was used as a negative electrode and the lowerelectrode plate was used as a positive electrode.

The results are shown in Table 8 and FIG. 51.

TABLE 8 Length of Fineness Applied Type of fiber of fiber voltageCurrent fiber (mm) (d) (kV) (μA/cm²) rayon 0.1 3 2 3.1

Example30

A viscosity of a hydraulic oil at each shear rate and a current in thehydraulic oil were measured in the same manner as in Example 21, exceptthat an electrode plate having a honeycomb structure (thickness: 0.5 mm)shown in FIG. 53 was used as the upper electrode in place of the rayonflocked electrode. In the metallic electrode of honeycomb structure, thearea of the conductive portion was 33% of the whole area, the total areaof the hole portion was 67% of the whole area, and the hole portion wasnon-conductive.

The results are shown in Table 9 and FIG. 52.

TABLE 9 Thickness Area of of conductive Applied Type of electrodeportion voltage Current electrode (mm) (%) (kV) (μA/cm²) honeycomb 0.533 2 0.1 electrode

What is claimed is:
 1. A micropump comprising an electro-sensitivemovable fluid and at least two electrodes which are arranged in such amanner that the electro-sensitive movable fluid is moved in thedirection of one electrode to the other electrode upon application of avoltage, said electrodes comprising ring electrodes through which theelectro-sensitive movable fluid is able to pass and which are arrangedin series so as to be insulated from each other.
 2. The micropump asclaimed in claim 1, wherein the electro-sensitive movable fluidcomprises a compound having at least one ester linkage in the molecule.3. The micropump as claimed in claim 1, wherein the electrodes are jetflow-producing electrodes capable of forming a non-uniform electricfield in the electro-sensitive movable fluid.
 4. The micropump asclaimed in claim 1, wherein the ring electrode has an electrodeprotrusion which protrudes toward the downstream side of the jet flow ofthe electro-sensitive movable fluid and serves to guide theelectro-sensitive movable fluid in the direction of one ring electrodeto the next ring electrode.
 5. The micropump as claimed in claim 4,wherein said electrode protrusion is needle-shaped.
 6. The micropump asclaimed in to 1, wherein the ring electrode comprises a cylindrical bodyand an electrode protrusion which protrudes from an edge of thecylindrical body toward the downstream side of the jet flow of theelectro-sensitive movable fluid.
 7. The micropump as claimed in claim 1,wherein said micropump is an electro-sensitive movable fluid circulatingpump, an electro-sensitive movable fluid discharge pump or anelectro-sensitive movable fluid transfer pump.
 8. The micropump asclaimed in claim 1, wherein the electro-sensitive movable fluidcomprises a compound having a conductivity σ and a viscosity η locatedon or inside a triangle in a graph showing a relation between aconductivity σ, plotted as abscissa, and a viscosity η, plotted asordinate, of a fluid at the working temperature, said triangle having,as vertexes, a point P indicated by the conductivity σ=4×10⁻¹⁰ S/m andthe viscosity η=1×10° Pa·s, a point Q indicated by the conductivityσ=4×10⁻¹⁰ S/m and the viscosity η=1×10⁻⁴ Pa·s, and a point R indicatedby the conductivity σ=5×10⁻⁶ S/m and the viscosity η=1×10⁻⁴ Pa·s, orcomprises a mixture of two or more kinds of compounds, said mixturebeing adjusted to have a conductivity σ and viscosity η located on orinside said triangle.
 9. The micropump as claimed in claim 1, wherein atleast one of said electrodes comprises a nozzle electrode arranged toprovide a tip for said micropump.
 10. A method of using a micropump,comprising the steps of arranging at least two electrodes in such amanner that an electro-sensitive movable fluid is moved in the directionof one electrode to the other electrode upon application of a voltage,then applying a voltage to the micropump containing theelectro-sensitive movable fluid, and producing a jet flow of theelectro-sensitive movable fluid in the direction of a target, whereinsaid electrodes comprise ring electrodes through which theelectro-sensitive movable fluid is able to pass and which are arrangedin series so as to be insulated from each other.
 11. The method of usinga micropump as claimed in claim 10, wherein the temperature of thetarget to which the jet flow is directed is different from thetemperature of the electro-sensitive movable fluid which forms the jetflow, and wherein heat energy exchange is carried out between the jetflow of the electro-sensitive movable fluid and the target when they arebrought into contact with each other.